假设变量veh是类Car的一个实例，我们可以调用veh.move()，是因为面向对象编程有（ ）性质。
class Vehicle {private: string brand; public: Vehicle(string b) : brand(b) {} void setBrand(const string& b) { brand = b; } string getBrand() const { return brand; } void move() const { cout << brand << " is moving..." << endl; }}; class Car : public Vehicle {private: int seatCount; public: Car(string b, int seats) : Vehicle(b), seatCount(seats) {} void showInfo() const { cout << "This car is a " << getBrand() << " with " << seatCount << " seats." << endl; }};