第1个回答 2009-03-21
It must have rained, didn't it?
这里的must have done 结构表示对过去事情的肯定推测,所以反义疑问部分用一般过去时的否定形式didn't。
第2个回答 2009-03-21
It must have rained, didn't it?
这里主句must have done表示对于过去的推测
所以用一般过去式提问本回答被提问者采纳
第3个回答 2009-03-21
haven't it
must表示肯定的猜测 如用mustn't表示不准
例 He must be at home,isn't he?
You must have finished your homework,haven't you?
但如果有表过去的时间状语,如yesterday last week 用过去式
第4个回答 2009-03-21
It must have rained, didn't it?