Question

It must have rained yesterday,____?

A.must it B mustn't C.did it D.didn't it 加知识点

Answer 1

应该是didn't it

对已发生的过去情况的推测，若陈述句谓语部分有“must have done”，而且有表示过去的时间状语，问句部分用didn't；若没有表示过去的时间状语，问句部分用haven't或hasn't。如：
1)They must have gone there last night,didn't they?
2)They must have arrived by now,haven't they?（根据by now来判断）
3)They must have been to the Great Wall,haven't they?

追问

为什么不用 Must it

追答

后面给你解释了呀

Answer 2

这是因为：must
have
done
的意思是一种推测：
句子意思是：地面是潮湿的，一定（偏肯定的推测）是昨天下了雨！
如果你must
,是作一定下了，没有推测的意思！