谁能帮我讲解一下when,while,as?when,while,as不是都可以表示……的时候吗?它们有什么区别么?用法有什么具体的要求?比如这道题：We are just on the point of calling you up ___ you come in.后面用的是come in,为

谁能帮我讲解一下when,while,as?when,while,as不是都可以表示……的时候吗?它们有什么区别么?用法有什么具体的要求?比如这道题：We are just on the point of calling you up ___ you come in.后面用的是come in,为
谁能帮我讲解一下when,while,as?
when,while,as不是都可以表示……的时候吗?它们有什么区别么?用法有什么具体的要求?
比如这道题：We are just on the point of calling you up ___ you come in.
后面用的是come in,为什么只能填when呢?

谁能帮我讲解一下when,while,as?when,while,as不是都可以表示……的时候吗?它们有什么区别么?用法有什么具体的要求?比如这道题：We are just on the point of calling you up ___ you come in.后面用的是come in,为
1.当从句中的谓语动词是持续性的动作时,我们可以用while,when或as.
While / When / As I was walking down the street,I noticed a police car in front of the bank.我顺着马路往前走时,发现银行门前停着一辆警车.
2.当从句中的谓语动词表示瞬间动作时,不可用while.
He was on the point of leaving when someone knocked at the door.他正要走,这时有人敲门.
3.如果谈论两个长动作,最常用的是while.
While John was sitting biting his nails,I was working out a plan to get us home.约翰坐在那里咬指甲时,我想出了一个回家的办法.
不过,as是可以用来说明两种正在发展或变化的情况的,这时as引导一个持续性的动作,主句中的动作与之同时进行.
As we talked on,he got more and more excited.我们继续往下谈的时候,他越来越兴奋.
4.如果表示两个短动作或事件同时发生,最常用的是as或just as,也可用when.
Just as he caught the ball,there was a tearing sound.当他抓住球的时候,有一种撕裂的声音.
I thought of it just when you opened your mouth.就在你要说话的时候,我也想到了.
先看下面一道高考题:
—I'm going to the post office.
—________you're there,can you get me some stamps?
A.As B.WhileC.Because D.If
对连词的用法考查在每年高考题中均有涉及.Because引导原因状语从句,If引导条件状语从句,按题干提供的情景均不可取.While和As都能引导时间状语从句,极易混淆.As一般强调主句谓语动词与从句谓语动词动作的同时性,而While除可表示同时性外,还含有一个动作在另一个动作正在进行或持续过程中的某一时刻发生.再从题干所提供的情景判断,就可知道B为最佳答案.
while的用法可从下述几点理解与运用.
一、while意为“当……时候”,指一段时间,不能用来表示一个时间点.
While the discussion was still going on,George came in.当讨论还在进行时,乔治走了进来.
二、while意为“而;然而”,表示转折.
There're plenty of rain in the southeast,while there's little in the northeast.东南部雨量充足,而西北部则很少下雨.
三、while意为“虽然;尽管”,表示让步.
While I admit his good points,I can see his shortcomings.尽管我承认他的优点,但我还是能看到他的缺点.
四、while意为“只要”,表示条件.
We can surely overcome these difficulties while we are closely united.只要我们紧密地团结一致,一定能克服这些困难.
五、while从句中的省略.
当while从句中的主语与主句的主语一致,且含有be的某种形式时,从句中的主语连同be可同时省略.
While listening to the radio,she fell asleep.她在听收音机时睡着了.
While in London,he studied music and painting.在伦敦时,他学习音乐和绘画.
六、while可用作名词,意为“一会儿;一段时间”.
作名词用时,主要用于短语中:after a while “过了一会儿”; all the while “一直,始终”; a short / little while ago “刚才”; once in a while “偶尔,间或”; wait / rest(for) a while “等 / 休息一会儿”.
I haven't seen her for a long while.我好久没有看见她了.
Where have you been all this while?这一阵子你到哪去了?
He usually goes to work by bike,but once in a while he goes by bus.他通常骑自行车上班,但偶尔也乘公共汽车.
I looked everywhere for the letter,but it was in my pocket all the while.我到处找那封信,却不知它一直在我口袋里.

when，while，as引导时间状语从句的区别
when，while，as显然都可以引导时间状语从句，但用法区别非常大。
一、when可以和延续性动词连用，也可以和短暂性动词连用；而while和as只能和延续性动词连用。
① Why do you want a new job when youve got such a good one already？（get为短...

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when，while，as引导时间状语从句的区别
when，while，as显然都可以引导时间状语从句，但用法区别非常大。
一、when可以和延续性动词连用，也可以和短暂性动词连用；而while和as只能和延续性动词连用。
① Why do you want a new job when youve got such a good one already？（get为短暂性动词）你已经找到如此好的工作，为何还想再找新的？
②Sorry，I was out when you called me．（call为短暂性动词）对不起，你打电话时我刚好外出了。
③Strike while the iron is hot．（is为延续性动词，表示一种持续的状态）趁热打铁。
④ The students took notes as they listened．（listen为延续性动词）学生们边听课边做笔记。
二、when从句的谓语动词可以在主句谓语动作之前、之后或同时发生；while和as从句的谓语动作必须是和主句谓语动作同时发生。
1．从句动作在主句动作前发生，只用 when。
①When he had finished his homework，he took a short rest．（finished先发生）当他完成作业后，他休息了一会儿。
②When I got to the airport，the guests had left．（got to后发生）当我赶到飞机场时，客人们已经离开了。
2．从句动作和主句动作同时发生，且从句动作为延续性动词时，when，while，as都可使用。
①When ／While ／As we were dancing，a stranger came in．（dance为延续性动词）当我们跳舞时，一位陌生人走了进来。
②When ／While ／As she was making a phonecall，I was writing a letter．（make为延续性动词）当她在打电话时，我正在写信。
3．当主句、从句动作同时进行，从句动作的时间概念淡化，而主要表示主句动作发生的背景或条件时，只能用 as。这时，as常表示“随着……”；“一边……，一边……”之意。
① As the time went on，the weather got worse．（as表示“随着……”之意）
② The atmosphere gets thinner and thinner as the height increases．随着高度的增加，大气越来越稀薄。
③As years go by，China is getting stronger and richer．随着时间一年一年过去，中国变得越来越富强了。
④The little girls sang as they went．小姑娘们一边走，一边唱。
⑤The sad mother sat on the roadside，shouting as she was crying．伤心的妈妈坐在路边，边哭边叫。
4．在将来时从句中，常用when，且从句须用一般时代替将来时。
①You shall borrow the book when I have finished reading it．在我读完这本书后，你可以借阅。
②When the manager comes here for a visit next week，Ill talk with him about this．下周，经理来这参观时，我会和他谈谈此事。
三、when用于表示“一……就……”的句型中（指过去的事情）。
sb．had hardly（＝scarcely） done sth．when．．．＝Hardly ／ Scarcely had sb．done sth．when．．．
①I had hardly ／scarcely closed my eyes when someone knocked at the door．＝Hardly ／ Scarcely had I closed my eyes when someone knocked at the door．我刚一闭上眼，就有人在敲门了。
②I had hardly ／scarcely entered my room when the telephone rang．＝Hardly ／Scarcely had I entered my room when the telephone rang．我刚一走进房门，电话就响了

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