if,when,untill,before从句.doc

由when，before，until引导的时间状语从句：在句子中起时间状语作用的句子称为时间状语从句。时间状语从句可以放在句首，句中和句尾。引导时间状语的词有 when while as before after since until/till as soon as， once， each time, the moment, immediately, instantly 等（一） when引导的时间状语从句1）when 意为“当时”，引导时间状语从句，表示主句的动作和从句的动作同时或先后发生。When 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。 when I was wandering the street, I met her.我在街上徘徊的时候遇到了他。2）when可以和延续性动词连用，也可以和短暂性动词连用He was listening to music when I went in.当我进去的时候，他正在听音乐。I will visit my parents when I have time.我有空时会去看望我的父母。3）when用于表示“一就”的句型中（指过去的事情）。 sbhad hardly（scarcely） done sthwhenHardly Scarcely had sbdone sthwhen 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。 I had hardly scarcely entered my room when the telephone rangHardly Scarcely had I entered my room when the telephone rang我刚一走进房门，电话就响了when引导的时间状语从句，不得不提起as和while1）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。 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？ Sorry，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。 Strike 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。 The students took notes as they listened（listen为延续性动词）学生们边听课边做笔记。 2）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。 When 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。 When 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。 When 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。 When 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。 As the time went on，the weather got worse（as表示“随着”之意） The atmosphere gets thinner and thinner as the height increases随着高度的增加，大气越来越稀薄。 As 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。 The little girls sang as they went小姑娘们一边走，一边唱。 The 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。 You shall borrow the book when I have finished reading it在我读完这本书后，你可以借阅。 When 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。 （二）Before:引导的时间状语从句Before 意为“在 之前”，引导时间状语从句时，表示主句的动作在从句的动作发生之前。Before I could get in a word, he already gave orders.我还来不及插话， 他已经吩咐下去了。It was two years before we met again.两年后我们才再次见面。It will not be long before you regret what youve done.不久你就会为你的所作所为后悔的。（三）由till或until引导的时间状语从句till和until一般情况下两者可以互换，但是在强调句型中多用until。并且要注意的是：如果主句中的谓语动词是瞬时动词时，常用否定形式not until意为直到才 这时的until 可以用before 来替换；如果主句中的谓语动词是延续性动词时，常用肯定形式。I will stay here until you come back.我会待在这里，直到你回来。（stay 表示动作可以延续）He didnt leave home until his father came back.他直到父亲回来才离开家。（leave home 表示动作的不能延续）Please wait until I arrived.请在我到达之前等着我。（wait 表示动作可以延续）由if引导的条件状语从句引导条件状语从句最常用的连词是if，常见的if条件状语从句表示在某条件下，某事很可能发生，条件是可能存在的，主句中某种情况发生的概率也是很高的。如： If you ask him，he will help you如果你请他帮忙，他会帮你的。 If you fail in the exam，you will let him down如果你考试不及格，你会让他失望的。 If you have finished the homework， you can go home如果你作业做完了就可以回家了。 另外，if从句还表示不可实现的条件或根本不可能存在的条件，也就是一种虚拟的条件或假设。从句多用一般过去时或过去完成时，表示对现在或过去的一种假设。如： If I were you，I would invite him to the party如果我是你，我会邀请他参加聚会。 I would have arrived much earlier if I had not been caught in the traffic要不是交通堵塞，我本会来得早一些。另外你还要注意if 条件句的时态搭配1if从句用一般现在时，主句用一般将来时 If he runs hell get there in time. 如果他用跑的，他就会及时赶到那儿。The cat will scratch you if you pull her tail. 如果你拉猫的尾巴，它就会抓你。2if从句用一般现在时，主句用may/might/canIf the fog gets thicker the plane may/might be diverted. 如果雾在大一些，飞机可能就会改在别的机场降落。If it stops snowing we can go out. 如果雪停了，我们就可以出去。3if从句用一般现在时，主句用must/shouldIf you want to lose weight you must/should eat less bread. 如果你想减肥，你必须少吃面包。4if从句用一般现在时，主句用一般现在时If you heat ice it turns to water. (也可用will turn)如果把冰加热，它就会化成水。5if从句用现在进行时，主句用一般将来时If you are looking for Peter youll find him upstairs. 如果你是在找彼得，上楼就会找到他。6if从句用现在完成时，主句用一般将来时If you have finished dinner Ill ask the waiter for the bill. 如果你吃完了，我就叫服务生来算账注意 ：学习 if 引导的条件状语从句的用法,现在总结一下: if 条件句不一般,几个要点记心间; 条件句,放在前,逗号要放句中间。 条件句表可能，主句多用将来时； 条件句表事实，主句常用现在时。在 if 引导的条件状语从句中，如果从句谈论的是一个有可能发生的事实及其产生的相关的结果，主句用一般将来时态，从句用一般现在时态。如： We can walk there if we cant find a bus . If it rains tomorrow ,we will not go to the zoo. What will you do if you find a panda in danger.如果 if 条件句谈论的是重复发生和预示要发生的情景和事件，则主从句大多用一般现在时态。如： If bears are in danger ,they attack people.在 if 引导的条件状语从句中，if 和条件句位置灵活，可直接放在主句后面，若 if 条件句放句首， 从句后面要加逗号，和主句隔开。还要注意前后时态一致原则由if引导的宾语从句的用法1)if引导宾语从句时，作“是否”讲，常放在动词ask 、see 、say 、know和find out等后面。如： Nobody knows if it will rain tomorrow. 没有人知道明天是否下雨。 Lucy asked if they had a cotton sweater .露西问他们是否有棉制的羊毛衣。2)if引导宾语从句时，要注意三个方面，即连词、语序和时态。 if不能和that 或其它连词（副词）同时使用，也不能省去。如： 我不知道他今天是否会来。 误 I dont know that if he will come here today . 正 I dont know if he will come here today . 他走过来看看猫是否出了毛病。 误 He came to see what if there was wrong with his cat . 正 He came to see if there was wrong with his cat . 2) if引导的宾语从句时，虽具有疑问意义，但从句语序应用陈述句语序。如： Did you know the way to the hospital ? The old woman asked me . The old woman asked me .if I knew the way to the hospital .老妇人问我是否知道去医院的路。 3 )if引导的宾语从句应和主句的时态保持一致。即主句为一般现在时，从句用现在时任一种时态；主句为一般过去时，从句则用过去时中的任一种时态。如： I dont know if he has come here . 我不知道他是否来过这儿。 Tom asked if I had read the book . 汤姆问我是否看过这本书 。 If, when, before, until引导的从句练习题基础题一、 选择题（ ）1. If you _ to the party, youll have a great time. A. will go B. went C. go D. going（ ）2. I _ her the answer if she _me. A. can tell, will ask B. will tell, will ask C. would tell, ask D. will tell, asks（ ）3 What are you going to do tomorrow? -Well go to the library tomorrow if it _. A. isnt rain B. rain C. wont rain D. doesnt rain（ ）4Ill wake you up when he _back.A. will B. is going to come C. comes D. come（ ）5Can you tell me_ you were born, Betty?A. who B. what C. when D. that（ ）6The meeting didnt start_ everyone was there.A. because B. until C. why D. if（ ）7The boy _ to bed _ his mother came in.A. went not; until B. didnt go; after C. went; until D. didnt go; until（ ）8 Im sure hell come to see me before he _ Beijing.A. will leave B. is leaving C. leave D. leaves（ ）9When he got to the station, the train _.A. left B. had left C. leaves D. has left（ ）10We _ TV when the telephone _.A. watched; was ringing B. were watching; rang C. watch; rings D. are watching; rang答案：1-5：CDDCC 6-10：BDDB二、 句型转换1. Study hard, or you wont pass the exam. （同义句转换）If you study hard, you _ _ the exam.2. Take a taxi, and youll catch the train. （同义句转换）_ you _ a taxi, youll catch the train.3. If you go to bed early, you wont feel tired in the morning. （同义句转换）_ _ _ early, _ you wont feel tired in the morning.4. If you dont work hard, your teacher will probably be angry. （同义句转换）_ _, _ your teacher will probably be angry.5. Breathe deeply for one minute, and youll feel relaxed. （同义句转换）_ you _ deeply for one minute, you _ _ relaxed.答案：1. will pass 2. If, take 3. Go to bed, and 4. Work hard, or 5. If, breathe, will feel三、 完成句子1. 如果努力学习，你就会取得好成绩。If you_ _, you _ good _.2. 他如果看电视太久了，他的父母会不高兴。If he _ TV too much, his parents _ _ unhappy.3.如果他到的晚了会发生什么事情？What _ _ if he _ late?4. 如果我们为他组织生日聚会，大家都会来的。Everyone _ _ if we _a birthday party _ him.5. 如果明天不下雨，我会和你一起去公园的。If it _ _tomorrow, I _ go to the park _you.6. 如果她睡过头了，他就会旅游迟到的。He_ _ _ _the trip if she _ _ late.7. 如果他有空，他会帮助你的。If he _ _ , he _ _ you.8. 如果Tom考试不及格，他就没有机会上高中了。Tom _have the _to go to the high school if he _the exams.9. 明天如果下雨的话，我们将呆在家里。We _ _ at home if it _ tomorrow.10.如果你上课睡觉，老师会生气。If you_ in class,your teacher _ _ _ _ you.答案：1. study hard; ll get, grades 2. watches, will be 3. will happen, arrives4. will come, make, for 5. doesnt rain, will, with 6. will be late for , gets up 7. is free, will help 8. wont, chance, doesnt pass 9. will stay, rains 10. sleep, will be angry with 附加题：用动词的适当形式填空。1. If you _(feel) tired, you _ (have) to have a rest.2. Where _ he _(see) the film if he _(have) time?3. If there _(be) fewer trees, there _(be) more pollution.4. He _(dress) more casually if he _(not work) on weekends.5. If Marcia _(live) alone, she _(keep) a pet dog.6. Lana _(buy) a new dress if the old one _(be) out of style.7. The twins _(fight) if they_(argue).8. I _(have) a bake sale if I _(need) money for education.9. Peter _(send) me a beautiful souvenir（纪念品） if he _(tour) Spain.10. If Mr Green _(say) I am hard- working, my parents _(feel) glad.答案：1. feel, have 2. will, see, has 3. are , will be 4. will dress, doesnt work 5. lives, will keep 6. will buy, is 7. will fight, argue 8. will have, need9. will send, tours 10. says, will feel提高题1. It was quiet _ those big trucks started coming through the town.A. before B. after C. until D. unless2. It seemed only seconds _ the boy finished washing his face.A. when B. before C. after D. even if3. Hardly had he reached the school gate _ the bell rang.A. while B. when C. as D. as soon as4.We were told that we should follow the main road _ we reached the central railway station.A. whenever B. until C. while D. wherever5. I recognized you _ I saw you at the airport.A. the moment B. while C. after D. once6. He was about to go to bed _ the doorbell rang.A. while B. as C. before D. when7._I listen to your advice, I get into trouble.A. Every time B. When C. While D. Until8. _ John was watching TV, his wife was cooking.A. As B. As soon as C. While D. Till9. The children ran away from the orchard(果园) _ they saw the guard.A. the moment B. after C. before D. as10. No sooner had I arrived home _ it began to rain.A. when B. while C. as D. than11. Several weeks had gone by _ I realized the painting was missing.A. as B. before C. since D. when12. It _ long before we _ the result of the experiment.A. will not be; will know B. is; will know C. will not be ; know D. is; know13. What was the party like? -Wonderful. Its years _ I enjoyed myself so much.A. after B. before C. when D. since14. The new secretary is supposed to report to the manager as soon as she_.A. will arrive B. arrives C. is going to arrive D. is arriving15. _ got into the room _ the telephone rang.A. He hardly had; then B. Hardly had he; when C. He had not; then D. Not had he; when16. No sooner had he finished his talk _ he was surrounded by the workers.A. as B. then C. than D. when17. Did you remember to give Mary the money you owed her?-Yes, I gave it to her _ I saw her.A. while B. the moment C. suddenly D. once18. I thought her nice and honest _ I met her.A. first time B. for the first time C. the first time D. by the first time19. He will have learned English for eight years by the time he _ from the university next year.A. will graduate B. will have graduated C. graduates D. is to graduate20. The moment the 28th Olympic Games _ open, the whole world cheered.A. declared B. have been declared C. have declared D. were declared答案：CBBBA DACAD BCDBB CBCCD难题1.Wang Lin will come to see you _ he reaches this city.A, before B, while C as soon as 2.I wont believe that the five-year-old boy can read five thousand words _ I have tested him by myself.A until B after C if 3. I wont call him _ he call me first.A after B unless C if D when4. I wont go to bed _ my work is done.A until B as C when D before5. _ you agree or not, I shall pay him the price he asks.A if B whether C When D As 6. Some people want t go boating _ others want to goo fishing.A when B if C while D as7. _ tomorrow, I will ask him where he has been.A When he comes B While he comesC When he will come D While he will come 8._ my mother came back, I was