(7-1)定义了如下 的Father类和Derived类,则下面()语句是正确的。 abstract class Father { public abstract void call(); } class Derived extends Father { public void call() { } }
A、Father Obj = new Derived();
B、Derived Obj = new Father ();
C、Father Obj = new Father();
D、Derived Obj = new Derived ();