A.protected是成员访问修饰符
B.protected成员可在同一个类中或派生类中被访问
C.protected是把成员保护起来,让外界完全无法访问
D.protected是类的默认修饰符
A.private->protected->default->public
B.private->protected->public->public
C.private->default->protected->public
D.default->private->protected->public