A.No output is produced.       123
B.No output is produced.        234
C.No output is produced.       1234
D.An exception is thrown at runtime.        123
E.An exception is thrown at runtime.         234
F.An exception is thrown at runtime.        1234

A.A finalizer may NOT be invoked explicitly.
B.The finalize method declared in class Object takes no action.
C.super.finalize（）is called implicitly by any over riding finalize method.
D.The finalize method for a given objec twill be called no more than once by the garbage collector.
E.The order in which finalize will be called on two objects is based on the order in which the two objects became finalizable.