单项选择题
A.class A extends B B.class B implements A C.class A implements B D.class B extends A
A.importjava.applet.Applet; B.importjava.io.*; C.importjava.awt.event; D.importjava.lang.*
A.a0,a1,a2,a3 B.a[0],a[1],a[2],a[3] C.a[1],a[2],a[2],a[4] D.a[0],a[1],a[2],a[3],a[4]