Question

---Must I finish the book today?

---Yes, you ________, but you ________ finish it now. Have a rest first.

1. A.
   do; don't have to
2. B.
   do; mustn't
3. C.
   must; don't have to
4. D.
   must; mustn't

Answer 1

C
回答以must开头的疑问句，肯定回答仍用must，否定回答用needn't或don't have to，而不用mustn't．mustn't的意思是“不准，千万不能”，它与have to的否定形式doesn't (don't) have to有很大的差别，后者意为“不必，不一定要”．答案为C．