must have been doing的用法是怎样的可以详细讲解一下吗?最好附带例句

请过路高人谈一下must be doing 与 must have been doing 的用法. have been doing 的用法, He must have been的用法. 关于must have been的用法 讲解一下whose的用法,好像既能用人又能用物,最好有例句. have been doing与 have done的用法区别 have been doing have done 的用法和区别 讲一下have been的用法, 有must have been的用法么?虚拟语气里面? 求have been doing的意思和用法 Have been doing 的被动语态是? must be的用法和must have been的用法是什么?