Be careful! The ice is not thick enough. You’d better _______ on it.

A．skate                                                        B．not to skate 

C．not skate                                                  D．not skating

Be careful!The ice is not thick enough．You'd better ________ on it．

1. A.
   skate
2. B.
   not to skate
3. C.
   not skate
4. D.
   not skating