Question

Mary ______ be in London because I saw her in town just now.

1. A.
   mustn’t
2. B.
   isn’t able to
3. C.
   needn’t
4. D.
   can’t

Answer 1

D
考查情态动词。Can’t不可能，句意：玛丽不可能在伦敦，因为我刚刚在商业区看到她了。