Question

--Is Mr Hu in the reading room?

--No, he ________ be there. He has gone to Tianjin.

1. A.
   mustn't
2. B.
   needn't
3. C.
   won't
4. D.
   can't

Answer 1

D
表示“可能，或许”意思的情态动词有can和may，其否定形式是can't, mayn't。mustn't表示不可以，禁此；needn't表示将来某种不可能出现的状况。