应用多继承中虚拟基类的应用，掌握虚拟函数在多态性中的应用，掌握虚函数、纯虚函数、抽象类的概念，并能应用抽象类解决实际问题。-The application of multiple inheritance in virtual base class to master virtual function polymorphism in the master virtual function, the concept of pure virtual functions, abstract classes, and abstract classes can be applied to solve practical problems.