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

问题描述:

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

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...