问题详情

下面程序输出的结果是【 】。
include ＜iostream＞
using namespace std;
class A {
public:
virtual void show() {cout＜＜"A!";
};
class B: public A {
public:
void show() {cout ＜＜ "B!";}
};
class C: public B{
public:
void show(){cout ＜＜ "C!";}
};
void show_info(A &i) {i. show();}
void main() {
A ia; B ib; C ic; show_info(ia);show_info(ib); show_info(ic); }请帮忙给出正确答案和分析，谢谢！