He must be sleeping.与He must sleep.有什么区别

He must be sleeping.与He must sleep.有什么区别 must be和must have been有什么区别he must have been sleeping.为什么这里要用must have been而不用must be he must ( )here.《be》 He must be happy! -Hey,everybody is here except Tom.What's wrong -He must().He stayed up until 12 p.m.last nightA.be sleeping B.sleepC.forgetD.have slept He pretended to be sleeping when I came in．(to be sleeping ） you didn`t hear my knocking at the door; you______ soundly when i came in答案是must be sleeping 是否应是must have been sleeping I' m sure he must have been sleeping at the moment 的反义疑问句 反义疑问句该用哪个动词提问?句中并没出现IS,ARE,DID,DO这些?比如：I have to go now,don't 为什么是DON'T?You must be joking now,aren't you?为什么是AREN'T?He might be sleeping just now,wasn't he?没有WAS出现呀?It must ha He must be fun.何如改成一般疑问句?Must he be fun 还是Is he fun? He must be fun.何如改成一般疑问句?Must he be fun 还是Is he fun? 英语翻译he must be--------- ------------thirty years old He must be verg tired.变反意疑问句? He must be American等于什么 He seems to be sleeping,为什么有个be?sleep为什么加ing? He seems to be sleeping,为什么有个be?sleep为什么加ing? He seems to be sleeping,为什么有个be?sleep为什么加ing? he can't be reading这个句子的时态结构he can't be readinghe must be sleeping 我有点不太理解 这指的应该是正在进行时但是正在进行时的结构是be+V-ing形式 那么这种结构形式怎么解释呢?