Question

-Must we collect the waste paper and bottles now?

-________．You can do it after class．

1. A.
   Yes, you must
2. B.
   No, you needn't
3. C.
   Yes, you may
4. D.
   No, you mustn't

Answer 1

B
根据题意“不必现在做”可知用否定形式，而must的否定回答用needn't。