they must have lost your letter in the post.

题目

they must have lost your letter in the post.
They must have lost your letter in the post
改被动语态
your letter must have been lost by them in the post
1、有MUST的是什么时态.
2、MUST后不是直接跟动词原型吗.

答案

must have done sth.对过去情况的推测,本身有可能是过去时,也有可能是完成时.意为：肯定
如：
He has been to Beijing .-----He must have been to Beijing.(完成时）
It rained last night----It must have rained last night (过去时）
have 也是动词原形.