abstract class A { abstract void al(); void a2() { } } class B extends A { void a1() { } void a2() { } } class C extends B { void c1() { } } and: A x = new B(); C y = new C(); A z = new C(); Which four are valid examples of polymorphic method calls?()
- A x.a2();
- B z.a2();
- C z.c1();
- D z.a1();
- E y.c1();
- F x.a1();