题目内容：

he must have stad up last night,_____
是hasn't he还是didin't he?
能说明原因吗?

优质解答

应该是hasn't.must的反问句,不是用must,而是根据must后面动词的时态决定的,比如She must finish her homework every day,doesn't she?
这里就不能用mustn't she,根据finish判断是一般现在时,所以是doesn't she