单项选择题
A.MyClock operator + (MyClock,long); B.MyClock operator + (MyClock,MyClock); C.MyClock operator + (long,long); D.MyClock operator + (long,MyClock);
A.类Shape是虚基类 B.类Shape是抽象类 C.类Shape中的Draw函数声明有误 D.语句“Shape s;”能够建立Shape的一个对象s
A.类Person是类Undergraduate的基类 B.类Undergraduate从类Student公有继承 C.类Student是类Person的派生类 D.类Undergraduate是类Person的派生类