如:It must have rained last night, didn't it? must表示推测,而时间状语为last night,所以其反意疑问句类似于变 It rained last night,故答案为:didn't it?
同样,如果有明显的完成时的提示词,则其反意疑问句用have/has/haven't/hasn't. 再如:He can't have been to Beijing before, has he? 其实就是变:He hasn't been to Beijing before,所以答案是:has he?