#include &lt;iostream&gt;    #include &lt;algorithm&gt;    #include &lt;vector&gt;    using namespace std;    int main &#40;&#41;    &#123;        int first&#91;&#93; = &#123;5, 10, 15, 20, 25&#125;;        int second&#91;&#93; = &#123;50, 40, 30, 20, 10&#125;;        vector&lt;int&gt; v&#40;10&#41;;              vector&lt;int&gt; :: iterator it;        sort &#40;first, first + 5&#41;;           sort &#40;second, second + 5&#41;;         it = set_union &#40;first, first + 5, second, second + 5, v.begin&#40;&#41;&#41;;        cout &lt;&lt; int&#40;it - v.begin&#40;&#41;&#41;;        return 0;    &#125;
A. 6
B. 7
C. 8
D. 9
Answer:A
#include &lt;iostream&gt;    #include &lt;algorithm&gt;    #include &lt;vector&gt;    using namespace std;    int main &#40;&#41;    &#123;        int first&#91;&#93; = &#123;5, 10, 15, 20, 25&#125;;        int second&#91;&#93; = &#123;50, 40, 30, 20, 10&#125;;        vector&lt;int&gt; v&#40;10&#41;;              vector&lt;int&gt; :: iterator it;        sort &#40;first, first + 5&#41;;           sort &#40;second, second + 5&#41;;         it = set_union &#40;first, first + 5, second, second + 5, v.begin&#40;&#41;&#41;;        cout &lt;&lt; int&#40;it - v.begin&#40;&#41;&#41;;        return 0;    &#125;
A. 6 B. 7 C. 8 D. 9
Explanation:In this program, We used the union function to find the number of elements.