C++错误集锦之：error C2243: 'type cast' : conversion exists, but is inaccessible

class Dog:public Animal
{
public:
	Dog(){cout<<"dog constructor"<<endl;}
	virtual ~Dog(){cout<<"dog destructor"<<endl;}
	void cry() const{cout<<"dog cry..."<<endl;}
};

class Dog:Animal
{
public:
	Dog(){cout<<"dog constructor"<<endl;}
	virtual ~Dog(){cout<<"dog destructor"<<endl;}
	void cry() const{cout<<"dog cry..."<<endl;}
};