#include &lt;iostream&gt;    #include &lt;stack&gt;    using namespace std;    int main &#40;&#41;    &#123;        stack&lt;int&gt; mystack;        mystack.push&#40;10&#41;;        mystack.push&#40;20&#41;;        mystack.top&#40;&#41; -= 5;        cout &lt;&lt; mystack.top&#40;&#41; &lt;&lt; endl;        return 0;    &#125;
A. 10
B. 20
C. 13
D. 15
Answer:A
#include &lt;iostream&gt;    #include &lt;stack&gt;    using namespace std;    int main &#40;&#41;    &#123;        stack&lt;int&gt; mystack;        mystack.push&#40;10&#41;;        mystack.push&#40;20&#41;;        mystack.top&#40;&#41; -= 5;        cout &lt;&lt; mystack.top&#40;&#41; &lt;&lt; endl;        return 0;    &#125;
A. 10 B. 20 C. 13 D. 15
Explanation:In this program, We used top option and this will return the reference to the next element.