题目内容：

must have done
must have done 的用法详细说明.
可以归结为虚拟语气里面的么?
must have been down 是must have down 的被动语态么

优质解答

Must have done 表对过去的推测.
Must have been done 表对过去的被动推测.
例句,She must have loved deeply,so she was so hurt.她一定曾经爱的深,才会如此受伤.
She must have been loved too,so she didn't have any regrets.她一定被爱过,所以她无憾.