#include<iostream>

using namespace std;

class A
{
   public:
          virtual void fun1(){cout<<"A fun1"<<endl;}
          virtual void fun2(){cout<<"A fun2"<<endl;}
          void fun3(){cout<<"A fun3"<<endl;}
          void fun4(){cout<<"A fun4"<<endl;}
};

class B:public A
{public:
        virtual void fun1(){cout<<"B fun1"<<endl;}
        virtual void fun2(int x){cout<<"B fun2"<<endl;}
        virtual void fun3(){cout<<"B fun3"<<endl;}
        void fun4(){cout<<"B fun4"<<endl;}
};

      
int main()
{
A* p;
B b;
p=&b;
p->fun1();
p->fun2();
p->fun3();
p->fun4();
  
return 0;
}

答案是：
　　B fun1
    A fun2
    A fun3
    A fun4
为什么？

谢谢！