A . A、C-12-->VC-12-->TU-12-->TUG-2-->VC-3-->AU-4-->AUG
B . B、C-12-->VC-12-->TU-12-->VC2-->TUG-2-->TUG-3-->AU-4-->AUG
C . C、C-12-->VC-12-->TU-12-->TUG-2-->TUG-3-->VC-4-->AU-4-->AUG
D . D、C-12-->VC-12-->TU-12-->TUG-2-->VC-3-->TUG-3-->AU-4-->AUG