#include <iostream>
#include <vector>
#include <cstring>

using namespace std;
struct edge{
    int from;
    int to;
    int nxt;
    edge(int f,int t,int n):from(f),to(t),nxt(n){}
};
vector<edge> edges;
int egs[1005];
void addedge(int f,int t){
    edges.emplace_back(f,t,egs[f]);
    egs[f]=edges.size()-1;
}
bool aisspecial[1005];
bool bisspecial[1005];
int dfs(int num,int fa){
    if(aisspecial[num]){
        return num;
    }
    for(int i=egs[num];i!=-1;i=edges[i].nxt){
        if(edges[i].to==fa){
            continue;
        }
        int temp=dfs(edges[i].to,num);
        if(temp!=-1){
            return temp;
        }
    }
    return -1;
}
int main() {
    int t;
    cin>>t;
    while(t--){
        int n;
        memset(egs,-1,sizeof egs);
        edges.clear();
        memset(aisspecial,0,sizeof aisspecial);
        memset(bisspecial,0,sizeof bisspecial);
        cin>>n;
        for(int i=0;i<n-1;i++){
            int a,b;
            cin>>a>>b;
            addedge(a,b);
            addedge(b,a);
        }
        int k1,k2;
        cin>>k1;
        for(int i=0;i<k1;i++){
            int temp;
            cin>>temp;
            aisspecial[temp]=true;
        }
        cin>>k2;
        int starter=-1;
        for(int i=0;i<k2;i++){
            int temp;
            cin>>temp;
            if(starter==-1){
                starter=temp;
            }
            bisspecial[temp]=true;
        }
        cout<<"B "<<starter<<endl;
        cout.flush();
        cin>>starter;
        if(aisspecial[starter]){
            cout<<"C "<<starter<<endl;
            cout.flush();
        }
        else{
            int ans=dfs(starter,0);
            if(ans==-1){
                cout<<"C -1\n";
                cout.flush();
            }
            else{
                cout<<"A "<<ans<<endl;
                cout.flush();
                int fakeans;
                cin>>fakeans;
                if(bisspecial[fakeans]){
                    cout<<"C "<<ans<<endl;
                    cout.flush();
                }
                else {
                    cout<<"C -1\n";
                    cout.flush();
                }
            }
        }

    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, k, x, rt;
vector<int> g[N];
int v1[N], v2[N];

int dfs(int u, int fu){
    if(v1[u]) return u;
    for(int i = 0; i < g[u].size(); i++){
        int v = g[u][i];
        if(v == fu) continue;
        int res = dfs(v, u);
        if(res) return res;
    }
    return -1;
}

int main(){
    fio
    int T; cin >> T;
    while(T--){
        mem(v1, 0);
        mem(v2, 0);
        cin >> n;
        rep(i, 1, n) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            cin >> u >> v;
            g[u].pb(v);
            g[v].pb(u);
        }
        cin >> k;
        rep(i, 1, k) cin >> x, v1[x] = 1;
        cin >> k;
        rep(i, 1, k) cin >> x, v2[x] = 1;
        cout << "B " << x << endl;
        cin >> rt;
        if(v1[rt]){ cout << "C " << rt << endl; continue; }
        int u = dfs(rt, 0);
        if(u == -1){ cout << "C -1" << endl; continue; }
        cout << "A " << u << endl;
        int v; cin >> v;
        if(v2[v]){ cout << "C " << v << endl; continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, rt;
vector<int> g[N];
int v1[N], v2[N];

int dfs(int u, int fu){
    if(v1[u]) return u;
    for(int i = 0; i < g[u].size(); i++){
        int v = g[u][i];
        if(v == fu) continue;
        int res = dfs(v, u);
        if(res != -1) return res;
    }
    return -1;
}

int main(){
    fio
    int T; cin >> T;
    while(T--){
        mem(v1, 0);
        mem(v2, 0);
        cin >> n;
        rep(i, 1, N) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            cin >> u >> v;
            g[u].pb(v);
            g[v].pb(u);
        }
        int k, x;
        cin >> k;
        rep(i, 1, k) cin >> x, v1[x] = 1;
        cin >> k;
        rep(i, 1, k) cin >> x, v2[x] = 1;
        cout << "B " << x << endl;
        cin >> x;
        if(v1[x]){ cout << "C " << x << endl; continue; }
        x = dfs(x, 0);
        if(x == -1){ cout << "C -1" << endl; continue; }
        cout << "A " << x << endl;
        cin >> x;
        if(v2[x]){ cout << "C " << x << endl; continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, rt;
vector<int> g[N];
int v1[N], v2[N];

int dfs(int u, int fu){
    if(v1[u]) return u;
    for(int i = 0; i < g[u].size(); i++){
        int v = g[u][i];
        if(v == fu) continue;
        int res = dfs(v, u);
        if(res != -1) return res;
    }
    return -1;
}

int main(){
    int T; cin >> T;
    while(T--){
        mem(v1, 0);
        mem(v2, 0);
        cin >> n;
        rep(i, 1, N) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            cin >> u >> v;
            g[u].pb(v);
            g[v].pb(u);
        }
        int k, x, tmp = -1;
        cin >> k;
        rep(i, 1, k) cin >> x, v1[x] = 1;
        cin >> k;
        rep(i, 1, k){
            cin >> x;
            if(tmp == -1) tmp = x;
            v1[x] = 1;
        }
        cout << "B " << tmp << endl;
        cin >> rt;
        if(v1[rt]){ cout << "C " << rt << endl; continue; }
        int u; u = dfs(rt, 0);
        if(u == -1){ cout << "C -1" << endl; continue; }
        cout << "A " << u << endl;
        cin >> tmp;
        if(v2[tmp]){ cout << "C " << tmp << endl; continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, rt;
vector<int> g[N];
int v1[N], v2[N];

int dfs(int u, int fu){
    if(v1[u]) return u;
    for(int i = 0; i < g[u].size(); i++){
        int v = g[u][i];
        if(v == fu) continue;
        int res = dfs(v, u);
        if(res != -1) return res;
    }
    return -1;
}

int main(){
    int T; cin >> T;
    while(T--){
        mem(v1, 0);
        mem(v2, 0);
        cin >> n;
        rep(i, 1, N) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            cin >> u >> v;
            g[u].pb(v);
            g[v].pb(u);
        }
        int k, x, tmp = -1;
        cin >> k;
        rep(i, 1, k) cin >> x, v1[x] = 1;
        cin >> k;
        rep(i, 1, k){
            cin >> x;
            if(tmp == -1) tmp = x;
            v1[x] = 1;
        }
        cout << "B " << tmp << endl;
        cin >> rt;
        if(v1[rt]){ cout << "C " << rt << endl; continue; }
        int u; u = dfs(rt, 0);
        if(u == -1){ cout << "C -1" << endl; continue; }
        cout << "A " << u << endl;
        cin >> tmp;
        if(v2[tmp]){ cout << "C " << u << endl; continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, rt;
vector<int> g[N];
int v1[N], v2[N];

int dfs(int u, int fu){
    if(v1[u]) return u;
    for(int i = 0; i < g[u].size(); i++){
        int v = g[u][i];
        if(v == fu) continue;
        int res = dfs(v, u);
        if(res != -1) return res;
    }
    return -1;
}

int main(){
    int T; cin >> T;
    while(T--){
        mem(v1, 0);
        mem(v2, 0);
        cin >> n;
        rep(i, 1, N) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            cin >> u >> v;
            g[u].pb(v);
            g[v].pb(u);
        }
        int k, x, tmp;
        cin >> k;
        rep(i, 1, k) cin >> x, v1[x] = 1;
        cin >> k;
        rep(i, 1, k){
            cin >> x;
            v1[x] = 1;
        }
        cout << "B " << x << endl;
        cin >> rt;
        if(v1[rt]){ cout << "C " << rt << endl; continue; }
        int u = dfs(rt, 0);
        if(u == -1){ cout << "C -1" << endl; continue; }
        cout << "A " << u << endl;
        cin >> tmp;
        if(v2[tmp]){ cout << "C " << u << endl; continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, rt;
vector<int> g[N];
int v1[N], v2[N];

int dfs(int u, int fu){
    if(v1[u]) return u;
    for(int i = 0; i < g[u].size(); i++){
        int v = g[u][i];
        if(v == fu) continue;
        int res = dfs(v, u);
        if(res != -1) return res;
    }
    return -1;
}

int main(){
    fio
    int T; cin >> T;
    while(T--){
        mem(v1, 0);
        mem(v2, 0);
        cin >> n;
        rep(i, 1, n) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            cin >> u >> v;
            g[u].pb(v);
            g[v].pb(u);
        }
        int k, x;
        cin >> k;
        rep(i, 1, k) cin >> x, v1[x] = 1;
        cin >> k;
        rep(i, 1, k) cin >> x, v2[x] = 1;
        cout << "B " << x << endl;
        cin >> x;
        if(v1[x]){ cout << "C " << x << endl; continue; }
        x = dfs(x, 0);
        if(x == -1){ cout << "C -1" << endl; continue; }
        cout << "A " << x << endl;
        cin >> x;
        if(v2[x]){ cout << "C " << x << endl; continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, st, k, t;
vector<int> g[N];
int v1[N], v2[N];

int fa[N];
void bfs(int s){
    queue<int> q; q.push(s);
    fa[st] = s;
    while(!q.empty()){
        int u = q.front(); q.pop();
        if(v1[u]){
            st = u;
            return;
        }
        for(auto v : g[u]) if(v != fa[u]){
            fa[v] = u;
            q.push(v);
        }
    }
}

int main(){
    scanf("%d", &t);
    while(t--){
        scanf("%d", &n);
        mem(v1, 0);
        mem(v2, 0);
        rep(i, 1, n) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            scanf("%d%d", &u, &v);
            g[u].pb(v);
            g[v].pb(u);
        }
        scanf("%d", &k);
        rep(i, 1, k) scanf("%d", &x), v1[x] = 1;
        scanf("%d", &k);
        rep(i, 1, k){
            scanf("%d", &x);
            v2[x] = 1;
            st = x;
        }
        printf("B %d\n", st);
        fflush(stdout);
        st = -1;
        scanf("%d", &st);
        if(v1[st]){ printf("C %d\n", st); fflush(stdout); continue; }
        bfs(st);
        int ed;
        printf("A %d\n", st);
        fflush(stdout);
        scanf("%d", &ed);
        if(v2[rt] && v1[ed]){ printf("C %d\n", st) continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, st, k, t;
vector<int> g[N];
int v1[N], v2[N];

int fa[N];
void bfs(int s){
    queue<int> q; q.push(s);
    fa[st] = s;
    while(!q.empty()){
        int u = q.front(); q.pop();
        if(v1[u]){
            st = u;
            return;
        }
        for(int i = 0; i < g[u].size(); i++){
            int v = g[u][i];
            if(v != fa[u]){
                fa[v] = u;
                q.push(v);
            }
        }
    }
}

int main(){
    scanf("%d", &t);
    while(t--){
        scanf("%d", &n);
        mem(v1, 0);
        mem(v2, 0);
        rep(i, 1, n) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            scanf("%d%d", &u, &v);
            g[u].pb(v);
            g[v].pb(u);
        }
        scanf("%d", &k);
        int x;
        rep(i, 1, k) scanf("%d", &x), v1[x] = 1;
        scanf("%d", &k);
        rep(i, 1, k){
            scanf("%d", &x);
            v2[x] = 1;
            st = x;
        }
        printf("B %d\n", st);
        fflush(stdout);
        st = -1;
        scanf("%d", &st);
        if(v1[st]){ printf("C %d\n", st); fflush(stdout); continue; }
        bfs(st);
        int ed;
        printf("A %d\n", st);
        fflush(stdout);
        scanf("%d", &ed);
        if(v2[st] && v1[ed]){ printf("C %d\n", st); continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, k, x, rt;
vector<int> g[N];
int v1[N], v2[N];

void dfs(int u, int fu){
    if(v1[u]) return u;
    for(int i = 0; i < g[u].size(); i++){
        int v = g[u][i];
        if(v == fu) continue;
        int res = dfs(v, u);
        if(res) return res;
    }
    return 0;
}

int main(){
    fio
    int T; cin >> T;
    while(T--){
        mem(vis, 0);
        cin >> n;
        rep(i, 1, n) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            cin >> u >> v;
            g[u].pb(v);
            g[v].pb(u);
        }
        cin >> k;
        rep(i, 1, k) cin >> x, v1[x] = 1;
        cin >> k;
        rep(i, 1, k) cin >> x, v2[x] = 1;
        cout << "B " << x << endl;
        cin >> rt;
        if(v1[rt]){ cout << "C " << rt << endl; continue; }
        int u = dfs(rt, 0);
        if(u = -1){ cout << "C -1" << endl; continue; }
        cout << "A " << x << endl;
        int v; cin >> v;
        if(v2[v]){ cout << "C " << v << endl; continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, st, k;
vector<int> g[N];
int v1[N], v2[N];

int fa[N];
void bfs(int s){
    queue<int> q; q.push(s);
    fa[st] = s;
    while(!q.empty()){
        int u = q.front(); q.pop();
        if(v1[u]){
            st = u;
            return;
        }
        for(auto v : g[u]) if(v != fa[u]){
            fa[v] = u;
            q.push(v);
        }
    }
}

int main(){
    int T; scanf("%d", &T);
    while(T--){
        mem(v1, 0);
        mem(v2, 0);
        scanf("%d", &n);
        rep(i, 1, n) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            scanf("%d%d", &u, &v);
            g[u].pb(v);
            g[v].pb(u);
        }
        scanf("%d", &k);
        rep(i, 1, k) scanf("%d", &x), v1[x] = 1;
        scanf("%d", &k);
        rep(i, 1, k){
            scanf("%d", &x);
            v1[x] = 1;
            st = x;
        }
        printf("B %d\n", st);
        fflush(stdout);
        st = -1;
        scanf("%d", &st);
        if(v1[st]){ printf("C %d\n", st); fflush(stdout); continue; }
        bfs(st);
        int ed;
        printf("A %d\n", st);
        fflush(stdout);
        scanf("%d", &ed);
        if(v2[rt] && v1[ed]){ printf("C %d\n", st) continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, k, x, rt;
vector<int> g[N];
int v1[N], v2[N];

int dfs(int u, int fu){
    if(v1[u]) return u;
    for(int i = 0; i < g[u].size(); i++){
        int v = g[u][i];
        if(v == fu) continue;
        int res = dfs(v, u);
        if(res) return res;
    }
    return 0;
}

int main(){
    fio
    int T; cin >> T;
    while(T--){
        mem(v1, 0);
        mem(v2, 0);
        cin >> n;
        rep(i, 1, n) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            cin >> u >> v;
            g[u].pb(v);
            g[v].pb(u);
        }
        cin >> k;
        rep(i, 1, k) cin >> x, v1[x] = 1;
        cin >> k;
        rep(i, 1, k) cin >> x, v2[x] = 1;
        cout << "B " << x << endl;
        cin >> rt;
        if(v1[rt]){ cout << "C " << rt << endl; continue; }
        int u = dfs(rt, 0);
        if(u = -1){ cout << "C -1" << endl; continue; }
        cout << "A " << x << endl;
        int v; cin >> v;
        if(v2[v]){ cout << "C " << v << endl; continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, rt;
vector<int> g[N];
int v1[N], v2[N];

int dfs(int u, int fu){
    if(v1[u]) return u;
    for(int i = 0; i < g[u].size(); i++){
        int v = g[u][i];
        if(v == fu) continue;
        int res = dfs(v, u);
        if(res) return res;
    }
    return -1;
}

int main(){
    fio
    int T; cin >> T;
    while(T--){
        mem(v1, 0);
        mem(v2, 0);
        cin >> n;
        rep(i, 1, n) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            cin >> u >> v;
            g[u].pb(v);
            g[v].pb(u);
        }
        int k, x;
        cin >> k;
        rep(i, 1, k) cin >> x, v1[x] = 1;
        cin >> k;
        rep(i, 1, k) cin >> x, v2[x] = 1;
        cout << "B " << x << endl;
        cin >> rt;
        if(v1[rt]){ cout << "C " << rt << endl; continue; }
        int u = dfs(rt, 0);
        if(u == -1){ cout << "C -1" << endl; continue; }
        cout << "A " << u << endl;
        int v; cin >> v;
        if(v2[v]){ cout << "C " << v << endl; continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, rt;
vector<int> g[N];
int v1[N], v2[N];

int dfs(int u, int fu){
    if(v1[u]) return u;
    for(int i = 0; i < g[u].size(); i++){
        int v = g[u][i];
        if(v == fu) continue;
        int res = dfs(v, u);
        if(res != -1) return res;
    }
    return -1;
}

int main(){
    int T; cin >> T;
    while(T--){
        mem(v1, 0);
        mem(v2, 0);
        cin >> n;
        rep(i, 1, N) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            cin >> u >> v;
            g[u].pb(v);
            g[v].pb(u);
        }
        int k, x, tmp;
        cin >> k;
        rep(i, 1, k) cin >> x, v1[x] = 1;
        cin >> k;
        rep(i, 1, k){
            cin >> x;
            v2[x] = 1;
        }
        cout << "B " << x << endl;
        cin >> rt;
        if(v1[rt]){ cout << "C " << rt << endl; continue; }
        int u = dfs(rt, 0);
        if(u == -1){ cout << "C -1" << endl; continue; }
        cout << "A " << u << endl;
        cin >> tmp;
        if(v2[tmp]){ cout << "C " << u << endl; continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, k, x, rt;
vector<int> g[N];
int v1[N], v2[N];

int dfs(int u, int fu){
    if(v1[u]) return u;
    for(int i = 0; i < g[u].size(); i++){
        int v = g[u][i];
        if(v == fu) continue;
        int res = dfs(v, u);
        if(res) return res;
    }
    return 0;
}

int main(){
    fio
    int T; cin >> T;
    while(T--){
        mem(v1, 0);
        mem(v2, 0);
        cin >> n;
        rep(i, 1, n) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            cin >> u >> v;
            g[u].pb(v);
            g[v].pb(u);
        }
        cin >> k;
        rep(i, 1, k) cin >> x, v1[x] = 1;
        cin >> k;
        rep(i, 1, k) cin >> x, v2[x] = 1;
        cout << "B " << x << endl;
        cin >> rt;
        if(v1[rt]){ cout << "C " << rt << endl; continue; }
        int u = dfs(rt, 0);
        if(!u){ cout << "C -1" << endl; continue; }
        cout << "A " << x << endl;
        int v; cin >> v;
        if(v2[v]){ cout << "C " << v << endl; continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, k, x, rt;
vector<int> g[N];
int v1[N], v2[N];

int dfs(int u, int fu){
    if(v1[u]) return u;
    for(int i = 0; i < g[u].size(); i++){
        int v = g[u][i];
        if(v == fu) continue;
        int res = dfs(v, u);
        if(res) return res;
    }
    return -1;
}

int main(){
    fio
    int T; cin >> T;
    while(T--){
        mem(v1, 0);
        mem(v2, 0);
        cin >> n;
        rep(i, 1, n) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            cin >> u >> v;
            g[u].pb(v);
            g[v].pb(u);
        }
        cin >> k;
        rep(i, 1, k) cin >> x, v1[x] = 1;
        cin >> k;
        rep(i, 1, k) cin >> x, v2[x] = 1;
        cout << "B " << x << endl;
        cin >> rt;
        if(v1[rt]){ cout << "C " << rt << endl; continue; }
        int u = dfs(rt, 0);
        if(u == -1){ cout << "C -1" << endl; continue; }
        cout << "A " << x << endl;
        int v; cin >> v;
        if(v2[v]){ cout << "C " << v << endl; continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define fi first
#define se second
#define pi acos(-1.0)
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define mem(a,b) memset(a,b,sizeof(a))
#define pb push_back
#define mk mack_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int inf = 0x3f3f3f3f;
const db eps = 1e-12;
const int N = 1e3 + 5;
const int mod = 998244353;
int n, rt;
vector<int> g[N];
int v1[N], v2[N];

int dfs(int u, int fu){
    if(v1[u]) return u;
    for(int i = 0; i < g[u].size(); i++){
        int v = g[u][i];
        if(v == fu) continue;
        int res = dfs(v, u);
        if(res != -1) return res;
    }
    return -1;
}

int main(){
    int T; cin >> T;
    while(T--){
        mem(v1, 0);
        mem(v2, 0);
        cin >> n;
        rep(i, 1, N) g[i].clear();
        rep(i, 1, n-1){
            int u, v;
            cin >> u >> v;
            g[u].pb(v);
            g[v].pb(u);
        }
        int k, x;
        cin >> k;
        rep(i, 1, k) cin >> x, v1[x] = 1;
        cin >> k;
        rep(i, 1, k) cin >> x, v2[x] = 1;
        cout << "B " << x << endl;
        cin >> x;
        if(v1[x]){ cout << "C " << x << endl; continue; }
        x = dfs(x, 0);
        if(x == -1){ cout << "C -1" << endl; continue; }
        cout << "A " << x << endl;
        cin >> x;
        if(v2[x]){ cout << "C " << x << endl; continue; }
        cout << "C -1" << endl;
    }
    return 0;
}


#include<bits/stdc++.h>
using namespace std;

using u_counter_type = unsigned int;
using need_int = int;
using counter_type = int;
using MAIN = int;
#define int DontUseIntÉ
using ll = long long;

template<typename T>
using PairOf = pair<T,T>;

using Void = tuple<>;

struct BasicInitialization{
    BasicInitialization(){
        ios_base::sync_with_stdio(false);
    }
};
BasicInitialization __basic_initialization__;
namespace mytl{
template<typename T>
T power(T base, ll exponential, T unit=1){
    T res = unit;
    while(exponential > 0){
        if(exponential%2 == 1) res = res * base;
        base = base * base;
        exponential = exponential / 2;
    }
    return res;
}
}

namespace std{

template<typename T>
istream& operator>>(istream& is, optional<T>& x){
    if(!x.has_value()){
        T x_;
        is>>x_;
        x = x_;
    }
    return is;
}

istream& operator>>(istream& is, Void& x){
    return is;
}

template<typename P, typename Q>
istream& operator>>(istream& is, pair<P,Q> x){
    return is>>x.first>>x.second;
}

template<typename P, typename Q>
ostream& operator<<(ostream& os, const pair<P,Q>& x){
    os<<"("<<x.first<<", "<<x.second<<")";
    return os;
}

template<typename T, template<typename, typename...> typename Container>
ostream& operator<<(ostream& os, const Container<T>& x){
    os<<"{";
    bool first = true;
    for(const auto& elem : x){
        if(!first) os<<", ";
        os<<elem;
        first = false;
    }
    os<<"}";
    return os;
}

}

namespace mytl{

template<typename T, typename P=T>
T read(istream& is=cin){
    P a;
    is>>a;
    return T(a);
}

template<typename T, typename P, typename Q>
T read(istream& is=cin){
    P a;
    Q b;
    is>>a>>b;
    return T(a,b);
}

template<typename T, typename P, typename Q, typename R>
T read(istream& is=cin){
    P a;
    Q b;
    R c;
    is>>a>>b>>c;
    return T(a,b,c);
}

template<typename T, typename... Q, typename Container=vector<T>>
vector<T> readValues(ll n, istream& is=cin){
    vector<T> res;
    repeat(n, [&res](){
        res.push_back(read<T,Q...>());
    });
    return Container(res.begin(), res.end());
}

}

namespace mytl{

template<typename T>
void print(const T& x, ostream& os=cout){
    os<<x;
}

}
namespace mytl{

template<typename T>
struct Lazy : optional<T>{

    function<T()> f;

    Lazy(function<T()> f) : f{f}, optional<T>() {};

    T& value(){
        if(!this->has_value()){
            optional<T>::operator=(f());
        }
        return optional<T>::value();
    }

};

#define LAZY(val, tipe) mytl::Lazy<tipe>([&](){return (val);})

}
namespace mytl{

template<typename T>
T discrete_binary_search(function<bool(T)> f, T l, T r){
    if(!f(l)) return l;
    while(l < r){
        T pivot = (l+r)/2;
        if(!f(pivot)) r = pivot-1;
        else if(!f(pivot+1)) l = r = pivot;
        else l = pivot+1;
    }
    return l;
}

template<typename T>
T continuous_binary_search(function<bool(T)> f, T l, T r, need_int iterations){
    mytl::repeat(iterations,[&](){
        T pivot = (l+r)/2;
        if(f(pivot)) l = pivot;
        else r = pivot;
    });
    return l;
}
}
namespace mytl{
    template<ll MOD>
    struct TSModulo{
    private:
        ll val;

    public:
        static TSModulo inverse(TSModulo x){// asserting MOD is prime
            return power(x, MOD-2);
        };
        TSModulo(ll initVal) : val{(MOD + initVal%MOD)%MOD} {};
        TSModulo() : TSModulo(0) {}
        TSModulo& operator=(const TSModulo&) = default;

        ll get() const{ // no type cast operator to prevent accidentally turning into ordinary number
            return val;
        }

        //Unary operators
        TSModulo operator-() const{
            return TSModulo(-val);
        };
        TSModulo operator+() const{
            return TSModulo(+val);
        };

        //Binary operators on ordinary numbers
        TSModulo operator-(const ll& operand) const{
            return TSModulo(val-operand);
        };
        TSModulo operator+(const ll& operand) const{
            return TSModulo(val+operand);
        };
        TSModulo operator*(const ll& operand) const{
            return TSModulo(val*operand);
        };
        TSModulo operator/(const ll& operand) const{ //asserting MOD is prime
            return TSModulo(inverse(operand) * val);
        };

        //Binary operators on Modulo
        TSModulo operator-(const TSModulo& operand) const{
            return TSModulo(val-operand.get());
        };
        TSModulo operator+(const TSModulo& operand) const{
            return TSModulo(val+operand.get());
        };
        TSModulo operator*(const TSModulo& operand) const{
            return TSModulo(val*operand.get());
        };
        TSModulo operator/(const TSModulo& operand) const{ //asserting MOD is prime
            return TSModulo(val * inverse(operand));
        };
    };

    using Mod107 = TSModulo<1000000007LL>;

    template<ll MOD>
    ostream& operator<<(ostream& os, TSModulo<MOD> x){
        return os<<"("<<x.get()<<"%"<<MOD<<")";
    }

}
namespace mytl{

template<typename T>
struct LazyVector : vector<T>{
    typename vector<T>::reference operator[](counter_type i){
        if(i >= this->size()) this->resize(i+1);
        return vector<T>::operator[](i);
    }
};

template<typename K, typename T>
struct AssocVector : LazyVector<T>{
    LazyVector<bool> exists;
    typename vector<T>::reference operator[](counter_type i){
        exists[i] = true;
        return LazyVector<T>::operator[](i);
    }
    typename vector<T>::iterator find(counter_type i){
        if(!exists[i]) return this->end();
        else return this->begin() + i;
    }
};

template<template<typename, typename, typename...> typename Container, typename Key, typename Value>
bool has_key(Container<Key, Value>& container, Key key){
    return container.find(key) != container.end();
}

}
namespace mytl{
    struct Modulo{
        static ll global_mod;
    private:
        ll val;
    public:
        const ll MOD;
        Modulo(ll initMOD, ll initVal) : MOD{initMOD}, val{initVal} {
            val %= MOD;
            if(val < 0) val += MOD;
        };
        Modulo() : Modulo(global_mod, 0) {};

        static Modulo inverse(Modulo x){// asserting MOD is prime
            return power(x, x.MOD-2, x.unit());
        };
        Modulo unit() const{
            return Modulo(MOD, 1);
        }
        Modulo& operator=(const Modulo& operand){
            val = operand.val;
            return *this;
        };

        ll get() const{ // no type cast operator to prevent accidentally turning into ordinary number
            return val;
        }

        //Unary operators
        Modulo operator-() const{
            return Modulo(MOD, -val);
        };
        Modulo operator+() const{
            return Modulo(MOD, +val);
        };

        //Binary operators on ordinary numbers
        Modulo operator-(const ll& operand) const{
            return Modulo(MOD, val-operand);
        };
        Modulo operator+(const ll& operand) const{
            return Modulo(MOD, val+operand);
        };
        Modulo operator*(const ll& operand) const{
            return Modulo(MOD, val*operand);
        };
        Modulo operator/(const ll& operand) const{ //asserting MOD is prime
            return Modulo(MOD, val * inverse(Modulo(MOD, operand)).get());
        };

        //Binary operators on Modulo
        Modulo operator-(const Modulo& operand) const{
            return Modulo(MOD, val-operand.get());
        };
        Modulo operator+(const Modulo& operand) const{
            return Modulo(MOD, val+operand.get());
        };
        Modulo operator*(const Modulo& operand) const{
            return Modulo(MOD, val*operand.get());
        };
        Modulo operator/(const Modulo& operand) const{ //asserting MOD is prime
            return Modulo(MOD, val * inverse(operand).get());
        };

    };

    ll Modulo::global_mod = 1000000007LL;

    Modulo mod107(ll x){
        return Modulo(1000000007LL, x);
    }
    ostream& operator<<(ostream& os, Modulo x){
        return os<<"("<<x.get()<<"%"<<x.MOD<<")";
    }

}
namespace mytl {

template<class T>
struct Resetter;

template<class T>
Resetter<T>* global_resetter = new Resetter<T>;

template<class T>
struct Resetter {

    using State = pair<counter_type, T>;

    State* state = new State{0, T()};

    Resetter(){}
    Resetter(T value){
        state = new State{0, value};
    }

    void activate(){
        global_resetter<T> = this;
    }

    void reset(T value){
        *state = State{state->first+1, value};
    }

    struct Variable{

        State state;
        State& parent = *global_resetter<T>->state;

        Variable() : state{*global_resetter<T>->state} {}
        Variable(T value) : state{global_resetter<T>->state->first, value} {}
        Variable(State st) : state{st} {}
        Variable(T value, State& parent) : state{parent->first, value} {};

        bool fresh(){
            return state.first >= parent.first;
        }

        void overwrite(){
            state = parent;
        }

        bool refresh(){
            if(!fresh()) overwrite();
        }

        T get(){
            refresh();
            return state.second;
        }

        void survive(){
            state.first = parent.first;
        }

        void operator=(T new_value){
            state.second = new_value;
            survive();
        }

    };

};
}
namespace mytl{

template<typename N, typename E, template<typename, typename, typename...> typename C>
struct Container_Graph{
    template<typename A, typename B>
    using Container = C<A,B>;
    using Edge = E;
    using Node = N;
    struct Arm{
        Edge edge;
        Node node;
    };

    Container<Node,  vector<Arm> > container;

    optional<ll> n;
    Container_Graph(ll n={}) : n{n}, container() {}

    void newEdge(Node u, Node v, Edge edge=Void()){
        container[u].push_back({edge, v});
    }
    vector<Node> getNodes(){
        vector<Node> res;
        if(n.has_value()){
            for(ll i=1; i<=n.value(); i++) res.push_back(i);
        }
        else{
            for(auto& p : container){
                res.push_back(p.first);
            }
        }
        return res;

    }
    vector<Arm >& getEdges(Node node){
        return container[node];
    }
    vector<Node > getNeighbours(Node node){
        vector<Node> res;
        for(auto& arm : getEdges(node)){
            res.push_back(arm.node);
        }
        return res;
    }

};

using NormalSimpleGraph = Container_Graph<ll, Void, AssocVector>;

template<typename G>
void readNeighbourList(G& g, ll indexing=1){
    for(ll i : forrange(g.n.size(), indexing)){
        for(ll neig : readValues<ll>(read<ll>())){
            g.new_edge(i, neig);
        }
    }
}

template<typename G>
void readEdgeList(G& g, ll m, bool bidirectional=true){
    using Node = typename G::Node;
    using Edge = typename G::Edge;
    for(auto elem : readValues<tuple<Node, Node, Edge>, Node, Node, Edge >(m)){
        Node u, v;
        Edge edge;
        tie(u, v, edge) = elem;
        g.newEdge(u,v,edge);
        if(bidirectional) g.newEdge(v, u, edge);
    }
}

template<typename G, template<typename> typename Path>
struct Reaching{
    typename Path<G>::Info info;
    typename G::Node node;
    bool operator<(const Reaching& other) const {
        return info > other.info;
    }
};

template<
    typename G,
    template<typename> typename QP,
    template<typename> typename P,
    typename F=void(*)(typename P<G>::Info, typename G::Node)
>
typename G::template Container<typename G::Node, typename P<G>::Info> queue_graph_algorithm(
    G& g,
    vector<Reaching<G,P> > sources,
    F new_node_callback=[](typename P<G>::Info, typename G::Node){})
{

    using Path = P<G>;
    using Edge = typename G::Edge;
    using Node = typename G::Node;
    using Info = typename Path::Info;
    //using Option = pair<Info, Node>;
    using R = Reaching<G,P>;
    using QueuePolicy = QP<R>;
    using Queue = typename QueuePolicy::Queue;

    Queue q;
    for(R source : sources) QueuePolicy::push(q, source);
    typename G::template Container<Node, Info> d;
    while(!q.empty()){
        R akt = QueuePolicy::consume(q);

        if(has_key(d, akt.node)) continue;

        d[akt.node] = akt.info;

        new_node_callback(akt.info, akt.node);
        for(auto arm : g.getEdges(akt.node)) if(!has_key(d, arm.node)){
            QueuePolicy::push(q, {Path::append(akt.info, akt.node, arm.edge, arm.node), arm.node});
        }
    }
    return d;
}

template<
        typename G,
        template<typename> typename QP,
        template<typename> typename P,
        typename F=void(*)(typename P<G>::Info, typename G::Node)
>
typename G::template Container<typename G::Node, typename P<G>::Info> queue_graph_algorithm_from_single_source(
        G& g,
        typename P<G>::Info info,
        typename G::Node node,
        F new_node_callback=[](typename P<G>::Info, typename G::Node){})
{
    return queue_graph_algorithm<G,QP,P,F>(g, {{info,node}},new_node_callback);
}

template<typename T>
struct Priority{
    using Queue = priority_queue<T>;
    static T consume(Queue& q){
        auto res = q.top();
        q.pop();
        return res;
    }
    static void push(Queue& q, T new_option){
        q.push(new_option);
    }
};

template<typename T>
struct FIFO{
    using Queue = queue<T>;
    static T consume(Queue& q){
        auto res = q.front();
        q.pop();
        return res;
    }
    static void push(Queue& q, T new_option){
        q.push(new_option);
    }
};

template<typename T>
struct FILO{
    using Queue = stack<T>;
    static T consume(Queue& q){
        auto res = q.top();
        q.pop();
        return res;
    }
    static void push(Queue& q, T new_option){
        q.pop();
    }
};

template<typename G>
struct JustLength{
    using Info = typename G::Edge;
    static Info append(Info old_info, typename G::Node old_node, typename G::Edge e, typename G::Node n){
        return old_info + e;
    }
};

template<typename G>
struct SimpleJustLength{
    using Info = ll;
    static Info append(Info old_info, typename G::Node old_node, typename G::Edge e, typename G::Node n){
        return old_info + 1;
    }
};

template<typename G>
struct LengthAndLastNode{
    using Info = pair<ll, typename G::Node>;
    static Info append(Info old_info, typename G::Node old_node, typename G::Edge e, typename G::Node n){
        return {old_info + e, old_node};
    }
};

template<typename G>
struct SimpleLengthAndLastNode{
    using Info = pair<typename G::Edge, typename G::Node>;
    static Info append(Info old_info, typename G::Node old_node, typename G::Edge e, typename G::Node n){
        return {old_info + 1, old_node};
    }
};

}
namespace mytl{

template<typename T, typename R, typename F=function<R(T)> >
vector<R> fmap(F f, const vector<T>& t){
    vector<R> res;
    for(auto elem : t) res.push_back(f(elem));
    return res;
}

template<typename T>
vector<T> forrange(T n, T from){
    vector<T> res(n);
    iota(res.begin(), res.end(), from);
    return res;
}

template<typename F>
void repeat(need_int n, const F& callback){
    for(need_int _ : forrange(n,0)) callback();
}

template<typename T, template<typename, typename...> typename Container>
vector<PairOf<T&> > adjecent_pairs(Container<T>& c){
    vector<PairOf<T&> > res;
    optional<T*> prev_elem;
    for(auto& elem : c){
        if(prev_elem.has_value()){
            res.push_back({*prev_elem.value(), elem});
        }
        prev_elem = &elem;
    }
    return res;
}
#define WATCH(x) cout << (#x) << " is " << (x) << endl
}
namespace mytl{

struct Point{
    ll x, y;

    Point(ll x, ll y) : x{x}, y{y} {};
    Point(pair<ll,ll> initPair) : x{initPair.first}, y{initPair.second} {};

    pair<ll,ll> getPair(){//not introducing type cast operator for safety
        return {x,y};
    }

    //Unary operators
    Point operator-() const{
        return {-x, -y};
    }
    Point operator+() const{
        return {x,y};
    }

    static ll sgn(ll x){
        return (x > 0) - (x < 0);
    }

    //Binary operators on ordinary numbers
    Point operator*(const ll& operand) const{
        return {x*operand, y*operand};
    }

    //Binary operators on Point itself
    Point operator+(const Point& operand) const{
        return {x+operand.x, y+operand.y};
    }
    Point operator-(const Point& operand) const{
        return {x-operand.x, y-operand.y};
    }

    ll operator*(const Point& operand){ //vectorial product
        return x*operand.y - y*operand.x;
    }

    ll direction(const Point& a, const Point& b) const{
        return sgn((a - *this) * (b - *this));
    };
};

ll distance_squared(const Point& a, const Point& b){
    return (a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y);
}

double distance(const Point& a, const Point& b){
    return sqrt(distance_squared(a, b));
}

ll cartesian_distance(const Point& a, const Point& b){
    return abs(a.x - b.x) + abs(a.y - b.y);
}

typedef vector<Point> Poly;

bool inside(const Poly& poly, const Point& point, bool strict){ //assuming Poly is weakly convex
    ll prevdir = -2;
    for(ll i=0; i<poly.size(); i++){
        ll nexdindex = (i+1)%poly.size();
        ll dir = poly[i].direction(poly[nexdindex], point);
        if(dir == 0){
            if(strict) return false;
        }
        else{
            if(dir != prevdir && prevdir != -2) return false;
            prevdir = dir;
        }

    }
    return true;
}

}
namespace mytl{
template<class Op>
struct Node : Op::Range{
    using Range = typename Op::Range;
    using T = typename Op::T;
    using Change = typename Op::Change;
    using Range::singleton;
    using Range::inside;
    using Range::intersect;
    using Range::leftHalf;
    using Range::rightHalf;

    Node *left_child=NULL, *right_child=NULL;

    T partial;
    Change pending = Op::identity();

    Node(Range range) : Range(range), partial{Op::initial(range)} {};

    T query(Range range, Change change){
        return query_(range, change).first;
    }

    void add(Change change){
        pending = Op::push(pending, change);
    }

    void prepare(){
        if(!singleton()){
            if(left_child == NULL) left_child = (new Node(leftHalf()));
            if(right_child == NULL) right_child = (new Node(rightHalf()));
            left_child->add(pending);
            right_child->add(pending);
        }
        partial = Op::apply(*this, partial, pending);
        pending = Op::identity();
    }

    pair<T,T> query_(Range range, Change change){
        //cout<<range<<" "<<*this<<endl;
        prepare();
        if(inside(range)){
            add(change);
            prepare();
            return {partial, Op::zero()};
        }
        if(!intersect(range)){
            //cout<<"n"<<range<<" "<<*this<<endl;
            return {Op::zero(), partial};
        }

        auto from_left = left_child->query_(range, change);
        auto from_right = right_child->query_(range, change);
        //cout<<from_right.first<<endl;
        auto needed = Op::reduce(from_left.first, from_right.first), rest = Op::reduce(from_left.second, from_right.second);
        partial = Op::reduce(needed, rest);
        return {needed, rest};
    }

    T build_from(const function<T(ll)>& getter){
        prepare();
        pending = Op::identity();
        if(singleton()) partial = getter(this->l);
        else partial = Op::reduce(left_child->build_from(getter), right_child->build_from(getter));
        return partial;
    }

};

struct Range1D{

    ll l, r;

    Range1D(ll l, ll r): l{l}, r{r} {}

    ll span() const {
        return r-l+1;
    }
    bool singleton() const {
        return span() == 1;
    }
    Range1D leftHalf() const {
        return Range1D(l, (l+r)/2);
    }
    Range1D rightHalf() const {
        return Range1D((l + r)/2 + 1, r);
    }
    bool inside(const Range1D& other) const {
        return other.l <= l && r <= other.r;
    }
    bool intersect(const Range1D& other) const {

        return other.inside(*this)
             ||(other.l <= l && l <= other.r)
             ||(other.l <= r && r <= other.r);
    }
};

}

namespace mytl{
template<typename T_>
struct Add_Sum{
    using Range = Range1D;
    using T = T_;
    using Change = T_;

    static Change identity(){
        return 0;
    }

    static T zero(){
        return 0;
    }

    static T initial(Range r){
        return zero();
    }

    static T reduce(T a, T b){
        return a + b;
    }

    static T apply(Range r, T a, Change c){
        return a + r.span()*c;
    }

    static Change push(Change a, Change b){
        return a + b;
    }
};

template<typename T_>
struct Multiply_Sum{
    using Range = Range1D;
    using T = T_;
    using Change = T_;

    static Change identity(){
        return 1;
    }

    static T zero(){
        return 0;
    }

    static T initial(Range r){
        return r.span()*1;
    }

    static T reduce(T a, T b){
        return a + b;
    }

    static T apply(Range r, T a, Change c){
        return a*c;
    }

    static Change push(Change a, Change b){
        return a*b;
    }
};

}

namespace mytl{
/*
struct Custom_Op{
    using Range = _;
    using T = _;
    using Change = _;

    static Change identity(){
        return _;
    }

    static T zero(){
        return _;
    }

    static T initial(Range r){
        return _;
    }

    static T reduce(T a, T b){
        return _;
    }

    static T apply(Range r, T a, Change c){
        return _;
    }

    static Change push(Change a, Change b){
        return _;
    }

};
*/

}
namespace mytl{

template<typename T, T(*f)(T,T)>
struct Tracker : optional<T>{

    Tracker() : optional<T>() {};

    void update(T val){
        if(this->has_value()){
            optional<T>::operator=(f(this->value(), val));
        }
        else{
            optional<T>::operator=(val);
        }
    }
};

template<typename T>
T min(T a, T b){return std::min(a,b);}
template<typename T>
T max(T a, T b){return std::max(a,b);}
template<typename T>
T __gcd(T a, T b){return std::__gcd(a,b);}

}
namespace mytl{

template <template<typename, typename, typename...> typename C, typename Arg, typename R>
function<R (Arg)> memoize(R (*fn)(Arg)) {
    C<Arg, optional<R> > table;
    return [fn, table](Arg arg) mutable -> R {
        optional<R>& res = table[arg];
        if(!res.has_value()){
            res = fn(arg);
        }
        return res.value();
    };
}

}

using G = mytl::Container_Graph<ll, Void, mytl::AssocVector>;

void processs(){
    ll n;
    cin>>n;
    G g(n);
    mytl::readEdgeList(g, n-1);

        //cout<<"hh";
    auto enyem_ = mytl::readValues<ll>(mytl::read<ll>());
    set<ll> enyem(enyem_.begin(), enyem_.end());
    auto ove_ = mytl::readValues<ll>(mytl::read<ll>());
    set<ll> ove(ove_.begin(), ove_.end());

    //cout<<enyem<<" "<<ove<<endl;
    auto ask = [&](ll& ide, char tipus, ll ki) -> bool{
        cout<<tipus<<" "<<ki<<endl;
        ll got;
        cin>>got;
        if(tipus == 'A' && mytl::has_key(ove, got)){
            cout<<"C "<<ki<<endl;
            return true;
        }
        if(tipus == 'B' && mytl::has_key(enyem, got)){
            cout<<"C "<<got<<endl;
            return true;
        }
        ide = got;
        return false;

    };

    ll one_piece;
    if(ask(one_piece, 'B', *ove.begin())) return;
     vector<pair<pair<ll,ll>, ll> > sour{{{0,-1}, *enyem.begin()}};
    // cout<<sour<<endl;
   auto tb = mytl::queue_graph_algorithm<G, mytl::AlgoComposer<mytl::FILO,mytl::SimpleLengthAndLastNode>::A >(g,sour);

    while(!mytl::has_key(enyem, one_piece)){
        one_piece = tb[one_piece].second;
    }

    ll dc;
    if(ask(dc, 'A', one_piece)) return;
    else{
        cout<<"C -1"<<endl;
    }

}

MAIN main(){
    ll T;
    cin>>T;
    mytl::repeat(T, [&](){
        processs();
    }) ;
}


#include<bits/stdc++.h>
using namespace std;

using u_counter_type = unsigned int;
using need_int = int;
using counter_type = int;
using MAIN = int;
#define int DontUseIntÉ
using ll = long long;

template<typename T>
using PairOf = pair<T,T>;

using Void = tuple<>;

struct BasicInitialization{
    BasicInitialization(){
        ios_base::sync_with_stdio(false);
    }
};
BasicInitialization __basic_initialization__;
namespace mytl{

template<typename T, typename R, typename F=function<R(T)> >
vector<R> fmap(F f, const vector<T>& t){
    vector<R> res;
    for(auto elem : t) res.push_back(f(elem));
    return res;
}

template<typename T>
vector<T> forrange(T n, T from){
    vector<T> res(n);
    iota(res.begin(), res.end(), from);
    return res;
}

template<typename F>
void repeat(need_int n, const F& callback){
    for(need_int _ : forrange(n,0)) callback();
}

template<typename T, template<typename, typename...> typename Container>
vector<PairOf<T&> > adjecent_pairs(Container<T>& c){
    vector<PairOf<T&> > res;
    optional<T*> prev_elem;
    for(auto& elem : c){
        if(prev_elem.has_value()){
            res.push_back({*prev_elem.value(), elem});
        }
        prev_elem = &elem;
    }
    return res;
}
#define WATCH(x) cout << (#x) << " is " << (x) << endl
}
namespace mytl{

template<typename T, T(*f)(T,T)>
struct Tracker : optional<T>{

    Tracker() : optional<T>() {};

    void update(T val){
        if(this->has_value()){
            optional<T>::operator=(f(this->value(), val));
        }
        else{
            optional<T>::operator=(val);
        }
    }
};

template<typename T>
T min(T a, T b){return std::min(a,b);}
template<typename T>
T max(T a, T b){return std::max(a,b);}
template<typename T>
T __gcd(T a, T b){return std::__gcd(a,b);}

}
namespace mytl{
template<typename T>
T power(T base, ll exponential, T unit=1){
    T res = unit;
    while(exponential > 0){
        if(exponential%2 == 1) res = res * base;
        base = base * base;
        exponential = exponential / 2;
    }
    return res;
}
}

namespace std{

template<typename T>
istream& operator>>(istream& is, optional<T>& x){
    if(!x.has_value()){
        T x_;
        is>>x_;
        x = x_;
    }
    return is;
}

istream& operator>>(istream& is, Void& x){
    return is;
}

template<typename P, typename Q>
istream& operator>>(istream& is, pair<P,Q> x){
    return is>>x.first>>x.second;
}

template<typename P, typename Q>
ostream& operator<<(ostream& os, const pair<P,Q>& x){
    os<<"("<<x.first<<", "<<x.second<<")";
    return os;
}

template<typename T, template<typename, typename...> typename Container>
ostream& operator<<(ostream& os, const Container<T>& x){
    os<<"{";
    bool first = true;
    for(const auto& elem : x){
        if(!first) os<<", ";
        os<<elem;
        first = false;
    }
    os<<"}";
    return os;
}

}

namespace mytl{

template<typename T, typename P=T>
T read(istream& is=cin){
    P a;
    is>>a;
    return T(a);
}

template<typename T, typename P, typename Q>
T read(istream& is=cin){
    P a;
    Q b;
    is>>a>>b;
    return T(a,b);
}

template<typename T, typename P, typename Q, typename R>
T read(istream& is=cin){
    P a;
    Q b;
    R c;
    is>>a>>b>>c;
    return T(a,b,c);
}

template<typename T, typename... Q, typename Container=vector<T>>
vector<T> readValues(ll n, istream& is=cin){
    vector<T> res;
    repeat(n, [&res](){
        res.push_back(read<T,Q...>());
    });
    return Container(res.begin(), res.end());
}

}

namespace mytl{

template<typename T>
void print(const T& x, ostream& os=cout){
    os<<x;
}

}
namespace mytl{

template<typename T>
struct Lazy : optional<T>{

    function<T()> f;

    Lazy(function<T()> f) : f{f}, optional<T>() {};

    T& value(){
        if(!this->has_value()){
            optional<T>::operator=(f());
        }
        return optional<T>::value();
    }

};

#define LAZY(val, tipe) mytl::Lazy<tipe>([&](){return (val);})

}
namespace mytl{

template<typename T>
T discrete_binary_search(function<bool(T)> f, T l, T r){
    if(!f(l)) return l;
    while(l < r){
        T pivot = (l+r)/2;
        if(!f(pivot)) r = pivot-1;
        else if(!f(pivot+1)) l = r = pivot;
        else l = pivot+1;
    }
    return l;
}

template<typename T>
T continuous_binary_search(function<bool(T)> f, T l, T r, need_int iterations){
    mytl::repeat(iterations,[&](){
        T pivot = (l+r)/2;
        if(f(pivot)) l = pivot;
        else r = pivot;
    });
    return l;
}
}
namespace mytl{
    template<ll MOD>
    struct TSModulo{
    private:
        ll val;

    public:
        static TSModulo inverse(TSModulo x){// asserting MOD is prime
            return power(x, MOD-2);
        };
        TSModulo(ll initVal) : val{(MOD + initVal%MOD)%MOD} {};
        TSModulo() : TSModulo(0) {}
        TSModulo& operator=(const TSModulo&) = default;

        ll get() const{ // no type cast operator to prevent accidentally turning into ordinary number
            return val;
        }

        //Unary operators
        TSModulo operator-() const{
            return TSModulo(-val);
        };
        TSModulo operator+() const{
            return TSModulo(+val);
        };

        //Binary operators on ordinary numbers
        TSModulo operator-(const ll& operand) const{
            return TSModulo(val-operand);
        };
        TSModulo operator+(const ll& operand) const{
            return TSModulo(val+operand);
        };
        TSModulo operator*(const ll& operand) const{
            return TSModulo(val*operand);
        };
        TSModulo operator/(const ll& operand) const{ //asserting MOD is prime
            return TSModulo(inverse(operand) * val);
        };

        //Binary operators on Modulo
        TSModulo operator-(const TSModulo& operand) const{
            return TSModulo(val-operand.get());
        };
        TSModulo operator+(const TSModulo& operand) const{
            return TSModulo(val+operand.get());
        };
        TSModulo operator*(const TSModulo& operand) const{
            return TSModulo(val*operand.get());
        };
        TSModulo operator/(const TSModulo& operand) const{ //asserting MOD is prime
            return TSModulo(val * inverse(operand));
        };
    };

    using Mod107 = TSModulo<1000000007LL>;

    template<ll MOD>
    ostream& operator<<(ostream& os, TSModulo<MOD> x){
        return os<<"("<<x.get()<<"%"<<MOD<<")";
    }

}
namespace mytl{

template<typename T>
struct LazyVector : vector<T>{
    typename vector<T>::reference operator[](counter_type i){
        if(i >= this->size()) this->resize(i+1);
        return vector<T>::operator[](i);
    }
};

template<typename K, typename T>
struct AssocVector : LazyVector<T>{
    LazyVector<bool> exists;
    typename vector<T>::reference operator[](counter_type i){
        exists[i] = true;
        return LazyVector<T>::operator[](i);
    }
    typename vector<T>::iterator find(counter_type i){
        if(!exists[i]) return this->end();
        else return this->begin() + i;
    }
};

template<template<typename, typename, typename...> typename Container, typename Key, typename Value>
bool has_key(Container<Key, Value>& container, Key key){
    return container.find(key) != container.end();
}

}
namespace mytl{
    struct Modulo{
        static ll global_mod;
    private:
        ll val;
    public:
        const ll MOD;
        Modulo(ll initMOD, ll initVal) : MOD{initMOD}, val{initVal} {
            val %= MOD;
            if(val < 0) val += MOD;
        };
        Modulo() : Modulo(global_mod, 0) {};

        static Modulo inverse(Modulo x){// asserting MOD is prime
            return power(x, x.MOD-2, x.unit());
        };
        Modulo unit() const{
            return Modulo(MOD, 1);
        }
        Modulo& operator=(const Modulo& operand){
            val = operand.val;
            return *this;
        };

        ll get() const{ // no type cast operator to prevent accidentally turning into ordinary number
            return val;
        }

        //Unary operators
        Modulo operator-() const{
            return Modulo(MOD, -val);
        };
        Modulo operator+() const{
            return Modulo(MOD, +val);
        };

        //Binary operators on ordinary numbers
        Modulo operator-(const ll& operand) const{
            return Modulo(MOD, val-operand);
        };
        Modulo operator+(const ll& operand) const{
            return Modulo(MOD, val+operand);
        };
        Modulo operator*(const ll& operand) const{
            return Modulo(MOD, val*operand);
        };
        Modulo operator/(const ll& operand) const{ //asserting MOD is prime
            return Modulo(MOD, val * inverse(Modulo(MOD, operand)).get());
        };

        //Binary operators on Modulo
        Modulo operator-(const Modulo& operand) const{
            return Modulo(MOD, val-operand.get());
        };
        Modulo operator+(const Modulo& operand) const{
            return Modulo(MOD, val+operand.get());
        };
        Modulo operator*(const Modulo& operand) const{
            return Modulo(MOD, val*operand.get());
        };
        Modulo operator/(const Modulo& operand) const{ //asserting MOD is prime
            return Modulo(MOD, val * inverse(operand).get());
        };

    };

    ll Modulo::global_mod = 1000000007LL;

    Modulo mod107(ll x){
        return Modulo(1000000007LL, x);
    }
    ostream& operator<<(ostream& os, Modulo x){
        return os<<"("<<x.get()<<"%"<<x.MOD<<")";
    }

}
namespace mytl {

template<class T>
struct Resetter;

template<class T>
Resetter<T>* global_resetter = new Resetter<T>;

template<class T>
struct Resetter {

    using State = pair<counter_type, T>;

    State* state = new State{0, T()};

    Resetter(){}
    Resetter(T value){
        state = new State{0, value};
    }

    void activate(){
        global_resetter<T> = this;
    }

    void reset(T value){
        *state = State{state->first+1, value};
    }

    struct Variable{

        State state;
        State& parent = *global_resetter<T>->state;

        Variable() : state{*global_resetter<T>->state} {}
        Variable(T value) : state{global_resetter<T>->state->first, value} {}
        Variable(State st) : state{st} {}
        Variable(T value, State& parent) : state{parent->first, value} {};

        bool fresh(){
            return state.first >= parent.first;
        }

        void overwrite(){
            state = parent;
        }

        bool refresh(){
            if(!fresh()) overwrite();
        }

        T get(){
            refresh();
            return state.second;
        }

        void survive(){
            state.first = parent.first;
        }

        void operator=(T new_value){
            state.second = new_value;
            survive();
        }

    };

};
}
namespace mytl{

template<typename N, typename E, template<typename, typename, typename...> typename C>
struct Container_Graph{
    template<typename A, typename B>
    using Container = C<A,B>;
    using Edge = E;
    using Node = N;
    struct Arm{
        Edge edge;
        Node node;
    };

    Container<Node,  vector<Arm> > container;

    optional<ll> n;
    Container_Graph(ll n={}) : n{n}, container() {}

    void newEdge(Node u, Node v, Edge edge=Void()){
        container[u].push_back({edge, v});
    }
    vector<Node> getNodes(){
        vector<Node> res;
        if(n.has_value()){
            for(ll i=1; i<=n.value(); i++) res.push_back(i);
        }
        else{
            for(auto& p : container){
                res.push_back(p.first);
            }
        }
        return res;

    }
    vector<Arm >& getEdges(Node node){
        return container[node];
    }
    vector<Node > getNeighbours(Node node){
        vector<Node> res;
        for(auto& arm : getEdges(node)){
            res.push_back(arm.node);
        }
        return res;
    }

};

using NormalSimpleGraph = Container_Graph<ll, Void, AssocVector>;

template<typename G>
void readNeighbourList(G& g, ll indexing=1){
    for(ll i : forrange(g.n.size(), indexing)){
        for(ll neig : readValues<ll>(read<ll>())){
            g.new_edge(i, neig);
        }
    }
}

template<typename G>
void readEdgeList(G& g, ll m, bool bidirectional=true){
    using Node = typename G::Node;
    using Edge = typename G::Edge;
    for(auto elem : readValues<tuple<Node, Node, Edge>, Node, Node, Edge >(m)){
        Node u, v;
        Edge edge;
        tie(u, v, edge) = elem;
        g.newEdge(u,v,edge);
        if(bidirectional) g.newEdge(v, u, edge);
    }
}

template<typename G, template<typename> typename Path>
struct Reaching{
    typename Path<G>::Info info;
    typename G::Node node;
    bool operator<(const Reaching& other) const {
        return info > other.info;
    }
};

template<
    typename G,
    template<typename> typename QP,
    template<typename> typename P,
    typename F=void(*)(typename P<G>::Info, typename G::Node)
>
typename G::template Container<typename G::Node, typename P<G>::Info> queue_graph_algorithm(
    G& g,
    vector<Reaching<G,P> > sources,
    F new_node_callback=[](typename P<G>::Info, typename G::Node){})
{

    using Path = P<G>;
    using Edge = typename G::Edge;
    using Node = typename G::Node;
    using Info = typename Path::Info;
    //using Option = pair<Info, Node>;
    using R = Reaching<G,P>;
    using QueuePolicy = QP<R>;
    using Queue = typename QueuePolicy::Queue;

    Queue q;
    for(R source : sources) QueuePolicy::push(q, source);
    typename G::template Container<Node, Info> d;
    while(!q.empty()){
        R akt = QueuePolicy::consume(q);

        if(has_key(d, akt.node)) continue;

        d[akt.node] = akt.info;

        new_node_callback(akt.info, akt.node);
        for(auto arm : g.getEdges(akt.node)) if(!has_key(d, arm.node)){
            QueuePolicy::push(q, {Path::append(akt.info, akt.node, arm.edge, arm.node), arm.node});
        }
    }
    return d;
}

template<
        typename G,
        template<typename> typename QP,
        template<typename> typename P,
        typename F=void(*)(typename P<G>::Info, typename G::Node)
>
typename G::template Container<typename G::Node, typename P<G>::Info> queue_graph_algorithm_from_single_source(
        G& g,
        typename P<G>::Info info,
        typename G::Node node,
        F new_node_callback=[](typename P<G>::Info, typename G::Node){})
{
    return queue_graph_algorithm<G,QP,P,F>(g, {{info,node}},new_node_callback);
}

template<typename T>
struct Priority{
    using Queue = priority_queue<T>;
    static T consume(Queue& q){
        auto res = q.top();
        q.pop();
        return res;
    }
    static void push(Queue& q, T new_option){
        q.push(new_option);
    }
};

template<typename T>
struct FIFO{
    using Queue = queue<T>;
    static T consume(Queue& q){
        auto res = q.front();
        q.pop();
        return res;
    }
    static void push(Queue& q, T new_option){
        q.push(new_option);
    }
};

template<typename T>
struct FILO{
    using Queue = stack<T>;
    static T consume(Queue& q){
        auto res = q.top();
        q.pop();
        return res;
    }
    static void push(Queue& q, T new_option){
        q.pop();
    }
};

template<typename G>
struct JustLength{
    using Info = typename G::Edge;
    static Info append(Info old_info, typename G::Node old_node, typename G::Edge e, typename G::Node n){
        return old_info + e;
    }
};

template<typename G>
struct SimpleJustLength{
    using Info = ll;
    static Info append(Info old_info, typename G::Node old_node, typename G::Edge e, typename G::Node n){
        return old_info + 1;
    }
};

template<typename G>
struct LengthAndLastNode{
    using Info = pair<ll, typename G::Node>;
    static Info append(Info old_info, typename G::Node old_node, typename G::Edge e, typename G::Node n){
        return {old_info + e, old_node};
    }
};

template<typename G>
struct SimpleLengthAndLastNode{
    using Info = pair<typename G::Edge, typename G::Node>;
    static Info append(Info old_info, typename G::Node old_node, typename G::Edge e, typename G::Node n){
        return {old_info + 1, old_node};
    }
};

}
namespace mytl{

struct Point{
    ll x, y;

    Point(ll x, ll y) : x{x}, y{y} {};
    Point(pair<ll,ll> initPair) : x{initPair.first}, y{initPair.second} {};

    pair<ll,ll> getPair(){//not introducing type cast operator for safety
        return {x,y};
    }

    //Unary operators
    Point operator-() const{
        return {-x, -y};
    }
    Point operator+() const{
        return {x,y};
    }

    static ll sgn(ll x){
        return (x > 0) - (x < 0);
    }

    //Binary operators on ordinary numbers
    Point operator*(const ll& operand) const{
        return {x*operand, y*operand};
    }

    //Binary operators on Point itself
    Point operator+(const Point& operand) const{
        return {x+operand.x, y+operand.y};
    }
    Point operator-(const Point& operand) const{
        return {x-operand.x, y-operand.y};
    }

    ll operator*(const Point& operand){ //vectorial product
        return x*operand.y - y*operand.x;
    }

    ll direction(const Point& a, const Point& b) const{
        return sgn((a - *this) * (b - *this));
    };
};

ll distance_squared(const Point& a, const Point& b){
    return (a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y);
}

double distance(const Point& a, const Point& b){
    return sqrt(distance_squared(a, b));
}

ll cartesian_distance(const Point& a, const Point& b){
    return abs(a.x - b.x) + abs(a.y - b.y);
}

typedef vector<Point> Poly;

bool inside(const Poly& poly, const Point& point, bool strict){ //assuming Poly is weakly convex
    ll prevdir = -2;
    for(ll i=0; i<poly.size(); i++){
        ll nexdindex = (i+1)%poly.size();
        ll dir = poly[i].direction(poly[nexdindex], point);
        if(dir == 0){
            if(strict) return false;
        }
        else{
            if(dir != prevdir && prevdir != -2) return false;
            prevdir = dir;
        }

    }
    return true;
}

}
namespace mytl{
template<class Op>
struct Node : Op::Range{
    using Range = typename Op::Range;
    using T = typename Op::T;
    using Change = typename Op::Change;
    using Range::singleton;
    using Range::inside;
    using Range::intersect;
    using Range::leftHalf;
    using Range::rightHalf;

    Node *left_child=NULL, *right_child=NULL;

    T partial;
    Change pending = Op::identity();

    Node(Range range) : Range(range), partial{Op::initial(range)} {};

    T query(Range range, Change change){
        return query_(range, change).first;
    }

    void add(Change change){
        pending = Op::push(pending, change);
    }

    void prepare(){
        if(!singleton()){
            if(left_child == NULL) left_child = (new Node(leftHalf()));
            if(right_child == NULL) right_child = (new Node(rightHalf()));
            left_child->add(pending);
            right_child->add(pending);
        }
        partial = Op::apply(*this, partial, pending);
        pending = Op::identity();
    }

    pair<T,T> query_(Range range, Change change){
        //cout<<range<<" "<<*this<<endl;
        prepare();
        if(inside(range)){
            add(change);
            prepare();
            return {partial, Op::zero()};
        }
        if(!intersect(range)){
            //cout<<"n"<<range<<" "<<*this<<endl;
            return {Op::zero(), partial};
        }

        auto from_left = left_child->query_(range, change);
        auto from_right = right_child->query_(range, change);
        //cout<<from_right.first<<endl;
        auto needed = Op::reduce(from_left.first, from_right.first), rest = Op::reduce(from_left.second, from_right.second);
        partial = Op::reduce(needed, rest);
        return {needed, rest};
    }

    T build_from(const function<T(ll)>& getter){
        prepare();
        pending = Op::identity();
        if(singleton()) partial = getter(this->l);
        else partial = Op::reduce(left_child->build_from(getter), right_child->build_from(getter));
        return partial;
    }

};

struct Range1D{

    ll l, r;

    Range1D(ll l, ll r): l{l}, r{r} {}

    ll span() const {
        return r-l+1;
    }
    bool singleton() const {
        return span() == 1;
    }
    Range1D leftHalf() const {
        return Range1D(l, (l+r)/2);
    }
    Range1D rightHalf() const {
        return Range1D((l + r)/2 + 1, r);
    }
    bool inside(const Range1D& other) const {
        return other.l <= l && r <= other.r;
    }
    bool intersect(const Range1D& other) const {

        return other.inside(*this)
             ||(other.l <= l && l <= other.r)
             ||(other.l <= r && r <= other.r);
    }
};

}

namespace mytl{
template<typename T_>
struct Add_Sum{
    using Range = Range1D;
    using T = T_;
    using Change = T_;

    static Change identity(){
        return 0;
    }

    static T zero(){
        return 0;
    }

    static T initial(Range r){
        return zero();
    }

    static T reduce(T a, T b){
        return a + b;
    }

    static T apply(Range r, T a, Change c){
        return a + r.span()*c;
    }

    static Change push(Change a, Change b){
        return a + b;
    }
};

template<typename T_>
struct Multiply_Sum{
    using Range = Range1D;
    using T = T_;
    using Change = T_;

    static Change identity(){
        return 1;
    }

    static T zero(){
        return 0;
    }

    static T initial(Range r){
        return r.span()*1;
    }

    static T reduce(T a, T b){
        return a + b;
    }

    static T apply(Range r, T a, Change c){
        return a*c;
    }

    static Change push(Change a, Change b){
        return a*b;
    }
};

}

namespace mytl{
/*
struct Custom_Op{
    using Range = _;
    using T = _;
    using Change = _;

    static Change identity(){
        return _;
    }

    static T zero(){
        return _;
    }

    static T initial(Range r){
        return _;
    }

    static T reduce(T a, T b){
        return _;
    }

    static T apply(Range r, T a, Change c){
        return _;
    }

    static Change push(Change a, Change b){
        return _;
    }

};
*/

}
namespace mytl{

template <template<typename, typename, typename...> typename C, typename Arg, typename R>
function<R (Arg)> memoize(R (*fn)(Arg)) {
    C<Arg, optional<R> > table;
    return [fn, table](Arg arg) mutable -> R {
        optional<R>& res = table[arg];
        if(!res.has_value()){
            res = fn(arg);
        }
        return res.value();
    };
}

}

using G = mytl::Container_Graph<ll, Void, mytl::AssocVector>;

void processs(){
    ll n;
    cin>>n;
    G g(n);
    mytl::readEdgeList(g, n-1);

        //cout<<"hh";
    auto enyem_ = mytl::readValues<ll>(mytl::read<ll>());
    set<ll> enyem(enyem_.begin(), enyem_.end());
    auto ove_ = mytl::readValues<ll>(mytl::read<ll>());
    set<ll> ove(ove_.begin(), ove_.end());

    //cout<<enyem<<" "<<ove<<endl;
    auto ask = [&](ll& ide, char tipus, ll ki) -> bool{
        cout<<tipus<<" "<<ki<<endl;
        ll got;
        cin>>got;
        if(tipus == 'A' && mytl::has_key(ove, got)){
            cout<<"C "<<ki<<endl;
            return true;
        }
        if(tipus == 'B' && mytl::has_key(enyem, got)){
            cout<<"C "<<got<<endl;
            return true;
        }
        ide = got;
        return false;

    };

    ll one_piece;
    if(ask(one_piece, 'B', *ove.begin())) return;
     vector<pair<pair<ll,ll>, ll> > sour{{{0,-1}, *enyem.begin()}};
    // cout<<sour<<endl;
   auto tb = mytl::queue_graph_algorithm<G, mytl::AlgoComposer<mytl::FILO,mytl::SimpleLengthAndLastNode>::A >(g,sour);

    while(!mytl::has_key(enyem, one_piece)){
        one_piece = tb[one_piece].second;
    }

    ll dc;
    if(ask(dc, 'A', one_piece)) return;
    else{
        cout<<"C -1"<<endl;
    }

}

MAIN main(){
    ll T;
    cin>>T;
    mytl::repeat(T, [&](){
        processs();
    }) ;
}