多态 C2

class apple {
public:
　　~apple(){ std::cout << "~apple()" << std::endl;}
};

class banana : public apple {
　　~banana(){ std::cout << "~banana()" << std::endl;}
};

class cat {
　　virtual ~cat(){ std::cout << "~cat()" << std::endl;}
}; 

class dog : public cat {
　　~dog(){ std::cout << "~dog" << std::endl;}
};

int main(void)
{
　　banana* pa1 = new banana;
　　delete pa1;

　　banana* pa2 = new banana;
　　delete (apple*)pa2;

　　dog* pd1 ＝ new dog;
　　delete pd1;

　　dog* pd2 = new dog;
　　delete (cat*)dog;　　
}