must表示推测有3种时态must be(现在),must be doing (现在正在),must have done

must have been doing与must have been done都表示推测,有什么区别呀? must have been done/must be done must be must have done 区别 用must be done 和must be doing 造句 must be done和 must have done区别 something must be done must be doing是对现在进行推测,那对将来呢/? You must be kidding 时态?是现在进行时态吗? must be和must have be有什么区别 all ( ) can be done must be done. must be 为什么要加ed以及must be done 和must be doing