— Must we wear our school uniform this afternoon?— No you. All of us will go on an outing

问题补充：

— Must we wear our school uniform this afternoon?

— No, you. All of us will go on an outing.

A. mustn

B. can

C. needn

D. couldn

答案：

A. mustn

B. can

(答案→)C. needn

D. couldn

解析：mustn 禁止；can 不能，不可能；needn 不必；couldn 不能。句意：我们必须今天下午穿上我们的校服吗？——不，你们不必。我们都要去郊游。must的含义是必须一定，其否定形式mustn’t表示禁止的含义。故must的否定回答一般借助于needn’和don’t have to来构成，结合语境可知选C.