when.while_as,since_的区别用法及练习题.doc

when,while,as,since的用法大总结以及练习题 一Since作为介词，后接某一确定的时间点，主句谓语动词是持续性动词，常与现在完成时态、现在完成进行时态或过去完成时态连用。例如： 1、He left the village in 1982 and I havent seen him since then.1982年他离开这个村子，从那以后我再没见过他。 2、Shes been working in a bank since leaving school.她中学毕业后就一直在一家银行工作。 3.He had spoken to her only once since the party. 自从那次聚会以来，他只跟她说过一次话。 二Since作为副词，表示从过去以来、以后或到现在的情形或状态，常与现在完成时态连用。例如： 1He left home two weeks ago and we havent heard from him since. 他两周前离开了家，到现在我们一直没有他的消息。 2He came to Zhenjiang 6 years ago and has lived here (ever) since.他6年前来到镇江，从此便住在这里。 三since引导原因状语从句 作为连词，since可引导原因状语从句，表示因为；既然；鉴于：例如： 1 He didnt come since he was busy.他因为忙，所以没有来。 2 Since this method doesnt work,lets try anoter.既然这种方法不行，我们就试用另一种吧。 四Since在特殊句型中的应用 句型I：“It is （has been）+时间+since+持续性动词的过去时”，表示“自从以来到现在已有多久。”例如： It has been quite some time since I was last in London.我上次离开伦敦至今颇有一段时间了。 句型II：“It was+时间+since+持续性动词的过去完成时”,表示“从到过去某时间点以来”，例如：It was three years since we had been here.那时我们在这已呆了三年。 六巩固练习 （一）单项选择1Do you smoke？_ Its two years since I smokedAYes，I do BNo，I dont CNot too much DOh，but I wish I didnt2Since you are busy, you _ tomorrow. A. dont need come B.need not come C. neednt come D.mustnt come 3.-Has he been home? -_,he _home since he graduated. A. No; hasnt been B.Yes;has been C.No; isnt D.Yes; is 4They _friends since they met in Shanghai. A.havent been B.have been C. arent D. are 5.I_here since he left the door open,but it seems that he wont come back today. A. have been waiting B.will have waited C.was waiting D.waited6.I _ from him since he has lived here. A. heard B. have heard C. have never heard D.have been hearing 7. He came to China _ 1998.A. from B. since C. at D. in8.- Excuse me.Did you notice whether the No.18 bus had gone by?-I dont know_ I began to stand here just now.A. as B.when C.since D.while现在完成进行时和现在完成时练习1. Im sure Andrew will win the first prize in the final. I think so. He _ for it for months. (2008江苏)A. is preparing B. was preparing C. had been preparing D. has been preparing2. By the time he realizes he _ into a trap, itll be too late for him to do anything about it. (2008山东) A. walks B. walked C. has walked D. had walked3. So far this year we _ a fall in house prices by between 5 and 10 percent. (2008福建) A. saw B. see C. had seen D. have seen4. Cathy is taking notes of the grammatical rules in class at Sunshine School, where she _ English for a year. (2007湖南) A. studies B. studied C. is studying D. has been studying 5. Danny _ hard for long to realize his dream and now he is popular. (2007福建)A. works B. is working C. has worked D. had worked DCDDCwhen, while和as的用法一when，while，as在时间状语从句中的区别：三者均可表示“当的时候”，如果主句表示的是短暂的动作，而从句表示的是一段时间，三者可通用。如：I met Kang Li aswhenwhile I was walking along the street当我沿街散步时碰见了康丽。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。 如： It was snowing when we got to the airport当我们到达机场时，天正下着雪。（不能用while） as强调主句与从句表示的动作同时发生，as常表示“随着”；“一边，一边；while强调主句表示的动作持续于while所指的整个时间内；when可指主、从句所述动作同时或先后发生。如：As the time went on，the weather got worse（as表示“随着”之意） He sang as he went along他边走边唱。Please write while I read我读的时候，请写下来。When he reached home，he had a little rest回到家后，他休息了一会儿。when用于表示“一就”的句型中（指过去的事情）。 somebody had hardly（scarcely） done whenHardly Scarcely had somebody done when I had hardly scarcely closed my eyes when someone knocked at the doorHardly 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。 二.when, while和as都可引导让步状语从句： when引导让步状语从句，意为“尽管，虽然”相当于though或although:They stopped trying when they might have succeeded next time. while引导让步状语从句，相当于although ，是较为正式的书面语:While I am willing to go, I would like it better that you went.as引导让步状语从句必须倒装，从句中的表语，状语或动词原形置于句首，若表语为名词，前置时省略冠词。 Child as he is, he knows a lot.Much as I like it, I will not buy it, for its too expensive.Try as he might, he couldnt find a job.三.when和while可用作并列连词:when作并列连词，意为“突然，正在那个时候”常运用于以下句型中：Somebody be about to dowhenSomebody be on the point of doingwhenSomebody be doing whenSomebody had donewhenWe were having a meeting when someone broke in.We were about to set off on our way, when it suddenly began to rain. 作并列连词，意为“而，却”，表示对比。He likes pop music, while I am fond of music.四.when和as用于原因状语从句中:when=since, now that “既然”Why do you want a new job when youve got such a good one already?意为“因为”，指说话双方都知道的原因。As he was not ready in time, we went without him.组题练习：1. Success came _ she began to play leading parts in radio plays.A. While B. as C. when D. if 2. The atmosphere gets thinner and thinner _ the height increases. A. When B. as C. while D. since 3. I was just about to go to sleep_ there was a loud knock on the door. A. While B. when C. as D. since4. They were surprised that a child should work out the problem_ they themselves couldnt.A. When B. where C. until D. while 5. We were swimming in the lake_ suddenly the storm started.A. When B. while C. until D. before 6. I do every single bit of housework_ my husband Bob just does the dishes now and then. (04高考广西卷)A. Since B. while C. when D. as 7. _ I accept that he is not perfect, I do actually like the person.(04高考江苏卷)A. While B. Since C. Before D. Unless8. Jasmine was holidaying with her family in a wildlife park_ she was bitten on the leg by a lion.(04高考上海卷) A. When B. while C. since D. once 9. _modeling business is by no means easy to get into, the good model will always be in demand.(o4高考浙江卷) A. While B. Since C. As D. If 10. All gases and most liquids and solids expand _ heated. A. as B. while C. before D. when11. We have only three books_ we need five. A. as if B. if C. when D. even though 12.How can we explain it to you_? A. while you are listening B. unless you will listen C. as you wont listen D. when you wont listen13._ I had to work to support my family.A. When I was a little child B. While I was a little child C. As I was a little child D. Before I was a little child14._, helicopters flew to the burning building. A. While the firefighters were trying to control the fire B. As the firefighters were trying to control the fire C. As soon as the firefighters were trying to control the fire D. After the firefighters had controlled the fire15. The husband was looking after the baby_. A. after his wife cooked in the kitchen B. as hi