有如下程序： #include ＜iostream.h＞ using namespace std; class Stack { public: Stack (unsigned n=10):size (n) {rep_=new int [size]; top=0;} Stack (stack&s}: size (s.size) { rep_new int[size]; for (int i=0;i＜size;i++ rip_[i]-s.rep_[i]; top=s.top; } ～Stack() {delete[]rep_;} void poush(int a) {rep_[topj=a; top++;} int pep() { --top; return rep_[top];} bool isEmpty() cons5 [return Top ==0;} private: int*rep_; unsigned size, top; }; int main() { Stack s1; for(int i=1;i＜5;i++) s1.push(i); Stack s2(s1); for(i=1;i＜3;i++} cout＜＜s2.pop()＜＜’,’; s2.push(6); s1.push(7); while(!s2.isEmpty()) cout＜＜s2.pop()＜＜’,’; return 0; } 执行上面程序的输出是
A．4,3,2,1,
B．4,3,6,7,2,1,
C．4,3,6,2,1,
D．1,2,3,4,