the river is dangerous.you ___ swim in it .A.can't B.mustn't C.couldn't D.needn't
问题描述:
the river is dangerous.you ___ swim in it .A.can't B.mustn't C.couldn't D.needn't
答
选择B,因为mustn't表示的是禁止,河是危险的,所以是禁止,表示命令