What are four valid examples of polymorphic method calls?()<br /> <img src="https://img.ppkao.com/2018-08/zhoulian/2018080113592779381.jpg" /><p> What are four valid examples of polymorphic method calls?()<br /> <img src="https://img.ppkao.com/2018-08/zhoulian/2018080113592779381.jpg" /></p>
A、A.x.a2();
B、B.z.a2();
C、C.z.c1();
D、D.z.a1();
E、E.y.c1();
F、F.x.a1();