——Mr John, we must hand in our homework today, ______? ……
20.——Mr John, we must hand in our homework today, ______?
——No, you _____. But you must bring it to school tomorrow.
A.needn’t we ; mustn’t
B.mustn’t we ; needn’t
C.mustn’t you ; mustn’t
D.needn’t we ; needn’t
解释所选的答案