We ________ last night, but we went to appreciate the flowerbeds and streetlights in Tiananmen Square instead．

1. A.
   might study
2. B.
   could study
3. C.
   should have studied
4. D.
   must have studied

We         last night, but we went to appreciate the flowerbeds and streetlights in Tiananmen Square instead.

A．might study         B．could study     C．should have studied     D．must have studied