Question

-Did they have a good time at the party?

-Judging by their smiles, they _________ have enjoyed themselves.

1. A.
   might
2. B.
   must
3. C.
   could
4. D.
   would

Answer 1

B
考查情态动词用法。Might have done 也许做了某事；must have done一定做了某事；could have done本可以做却未做；would have done会做某事；句意：—在聚会上你玩的开心吗？—从他们的微笑来看，他们一定完的很开心。