Der1 called! Der2 called! #include <iostream> using namespace std; class Base { public: __________;//(1)声明纯虚函数 5分 }; class Der1:public Base { public: void display(){ cout<<"Der1 called!"<<endl;} }; class Der2:public Base { public: void display() { cout<<"Der2 called!"<<endl;} }; void fun(________)(2)补充函数形参 5分 { p->display(); } int main() { Der1 b1; Der2 b2; Base * p=&b1; fun(p); _______（3）补充语句，完成动态多态 5分 fun(p); return 0; } （4）给出运行结果 5分

class Base {
public:
virtual void display() = 0; //(1)声明纯虚函数
};

void fun(Base *p) //(2)补充函数形参
{
p->display();
}

int main()
{
Der1 b1;
Der2 b2;

Base *p = &b1;
fun(p); //(3)补充语句，完成动态多态
p = &b2;
fun(p);

return 0;
}

//运行结果：
//Der1 called!
//Der2 called!