must be doing 与 must have been doing
请过路高人谈一下must be doing 与 must have been doing 的用法。
这是在新概念第九课出现的。
这里的 must 换成 shall 、could 、can 等意义上有什么变化吗？
must be doing:肯定某人正在做某事..He must be doing his homework.他一定在做他的作业
must have been doing:肯定某人一直在做的事..He must have been trying his best to study..他肯定一直都在尽力学习..
must表强烈的肯定，shall不那么强烈，could最弱..表推测的情况一般不用can ...
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must be doing- She must be doing her homework right now.
She must have been doing her chores for tomorrow..
must be doing 与 must have been doing
must be doing:肯定某人正在做某事..He must be doing his homework.他一定在做他的作业 must have been doing:肯定某人一直在做的事..He must have been trying his best to study..他肯定一直都在尽力学习..must表强烈的肯定，shall不那么强烈，could最弱..表推测的情况一般不用can ......
must be和must have been 在句子中作什么成份及其时态?
must be不一定是系动词，后面加doing是现在进行时。must have been 本身可以是现在完成时，后面加doing是现在完成进行时
情态动词的用法有哪些?
（1）情态动词+动词完成式: must have done （2）情态动词+动词进行式: must be doing （3）情态动词+动词完成进行式: must have been doing （4）某些情态动词的特殊用法: need 一、情态动词+动词完成式 情态动词+动词完成式即“情态动词+ have + done分词”，表示对过去行为或动作进行推测、评...
must be的用法
“must+be”“must+be+ v -ing”“must+表示状态的动词”可表示现在或一般的情况；“must+have”表示过去的情况；“must+表示动作的动词”表示将来的情况。must的英式读法是[mʌst]；美式读法是[mʌst]。单词直接源自古英语的moste，意为应当，必须，需。作助动词意思有必须；应当；很...
must have been doing
must have been doing意思是 一定一直都在做某事She is so tired .She must has been working all the morning.她很疲劳了她一定工作了一个早上。must have been doing 表示肯定的猜测 并且猜测这种动作,或者行为一直持续到现在 还有must have been done是must have done的被动形式。是对过去发生的...
情态动词表推测与虚拟语气为什么总容易混淆?
He must be sleeping.他现在一定是在睡觉.二、对发生完的事情的推测 1.must have done (...一定是做过.）He must have seen me before.以前他一定是见过我.You must have been to Shanghai.你一定是去过上海.2.must have been doing( 一定是正在做...)When you called me ,I must have ...
must have been driving用来表示什么肯定的推测?
must have been doing 这个结构表示对过去正在发生的动作的肯定推测 must have been driving 过去一定正在驾驶
must have been doing与must have been done都表示推测,有什么区别呀...
must have+ been doing 都知道be doing 表示正在进行的动作，正在发生的，那要放到must have done里面去，则要符合“done”的这中过去分词的形式，则就变成了must have+been doing 拉，有一直发生的意思，整个意思就是“表示对过去一直发生的事情的推测”。如：Tom must have been playing basketball....
must have been doing的用法
意思是 一定一直都在做某事 She is so tired .She must has been working all the morning.她很疲劳了 她一定工作了一个早上 must have been doing 表示肯定的猜测 并且猜测这种动作,或者行为一直持续到现在
mustbe和mustbedoing怎么区分?
区分must be和must be doing的关键在于理解它们表示的时间点和状态。must be强调一种确定的状态或存在，相当于“一定是...”。例如：Look at that man. He must be a thief. 看那个人，他一定是小偷。而must be doing则表示正在发生的行为，相当于“一定在做...”。例如：Look at that man. ...
