he must be helping the old man to water the flowers,

题目

he must be helping the old man to water the flowers,
Ais he Bisn't he Cmust he Dmustn't he

答案

选择B.must反义疑问句的详细用法讲解如下：当陈述部分有情态动词must,问句有4种情况：　　（1）mustn't表示“禁止,不可,不必”时,附加问句通常要用must.　　You mustn't stop your car here,must you?　　你不能把车...