请过路高人谈一下must be doing 与 must have been doing 的用法.

请过路高人谈一下must be doing 与 must have been doing 的用法. must have been doing与must have been done都表示推测,有什么区别呀? be always doing与have always been doing的区别 have been doing 的用法, must be do与must be doing 区别 选择：You have been doing washing all the morning.You must be t must be的用法和must have been的用法是什么? have been doing与 have done的用法区别 must be stopped from doing He must have been的用法. 关于must have been的用法 must have been done/must be done