选B.情态动词must在表示推测,意为”一定“时,其后的反意疑问句不用must,一般用其后的系动词或助动词.再如：He must be at home now,isn't he?He must have finished his homework,hasn't he?但是：He must have fini...He must have finished his homework yesterday, didn't he?请问为什么啊，O(∩_∩)O谢谢解答也就是说，在must后面接have+过去分词时，如果后面还有过去的时间状语，那么反义疑问句的构成就要用have后面的词，且是过去的形式。再如：She must have been a nurse, hasn't she?She must have been a nurse in the past, wasn't she?