问题补充：
--Must we hand in our homework now?---No, you . You hand them in before Friday.
A. mustn’t , can
B. needn’t, can
C. can , can
D. mustn’t, must
答案：
A. mustn’t , can
(答案→)B. needn’t, can
C. can , can
D. mustn’t, must
解析：must(必须),它的否定形式是needn’t,此处的can表示“可以”.
