资源描述
第一节情态动词和虚拟语气 (2) 考点一：情态动词1情态动词的类型和特征(1)情态动词的类型只作情态动词用的有：must，can(could)，may(might)，ought to。可作情态动词也可作实义动词的有：need，dare(美语中常用作实义动词)。可作情态动词也可作助动词的有：shall(should)，will(would)。具有情态动词的某些特征的有：have(had) to，used to。(2)情态动词的特征有一定的词义，但不能单独作谓语，它们要和行为动词或连系动词连用，构成谓语。适用于主语的各种人称和数(have to例外，主语是第三人称单数时，要用has to)。如：We/He must work hard.我们/他一定要努力工作。He has to walk home.他得步行回家。后面接动词原形，即不带to的不定式(ought to，have to, used to本身带有to)。如：He may lose his way.他可能会迷路。You ought to obey the law.你要遵守法律。具有助动词的作用，即可用来构成否定句、疑问句及用于简明答语。如：I cant swim. Can you swim?我不会游泳，你会游泳吗？No, I cant either.不，我也不会。2情态动词的基本用法及区别(1)can，could表示能力和客观可能性。如：Some of us can use the computer now，but we couldnt last year.现在我们中的一些人能使用电脑了，但去年我们还不能。It will be sunny in the daytime，but it could rain later on this evening.白天会天晴，但晚上可能会下雨。表示请求和允许。如：If you keep still, you can sit on either side of the boat.如果你保持不乱动，你可以坐在船的任一边。Can I come in?我能进来吗？Yes, you can.是的，你可以进来。表示请求，口语中常用could代替can，使语气更委婉，但主要用于疑问句。此类问句的答语不能用could，应该用can。如：Could I use your bike tomorrow morning?明天上午我可以用你的自行车吗？Yes, you can.(否定回答可用：No, Im afraid not.)是的，你可以。(不，恐怕不行。)表示惊异、怀疑(不相信)等态度，主要用于否定句、疑问句和感叹句中。如：How can you be so foolish?你怎么这么傻呢？They cant be working at this time of day.他们不可能在这个时候工作。can和be able to都表示能力，在意义上没有区别。但can只有现在时和过去时，而be able to则有更多的时态形式。在肯定句中，如果表示过去某时做成了某事，常用was/were able to，而不用could。如：The fire was very big but everyone was able to escape from the building.火很大，但每个人都成功逃出了那栋大楼。(2)may，might表示请求或允许。否定回答时，一般要用mustnt表示“禁止、阻止”之意。如：May I smoke here?我能在这抽烟吗？Yes, please./Certainly./Yes, you may./No, you mustnt.可以，请便。/当然可以。/是的，你可以。/不，你不能抽烟。表示可能性的推测，含有“或许”“可能”之意，用might代替may时，则语气显得更加不肯定。如：The news may not be true.这则新闻可能不是真的。He might have some fever.他或许发烧了。may可用来表示祝愿。如：May you be happy!祝你快乐！May you succeed!祝你成功！may as well表示“还是的好，不妨，最好，”如：You may as well tell me the truth.你不妨和我说实话。We may as well stay where we are.我们最好待在原地。(3)must，have to表示必须，其肯定回答用must，否定回答用neednt或dont have to。如：Must I finish the work today?我今天必须完成工作吗？Yes，you must./No，you neednt./You dont have to.是的，你必须完成。/不，你需要。/你不需要。must可表示肯定性的推测，意为“一定，准是”，只用于肯定句中。其否定形式为cant，表示不可能。如：You must be hungry after a long walk.走了这么远的路你一定饿了。must表示的是说话人的主观看法，而have to则往往强调客观需要。如：I must go now.我现在必须走了。I have to go now，because my mother is in hospital.我现在得走了，我母亲生病住院了。mustnt表示禁止、不许。如：You mustnt leave the room.你不允许离开房间。(4) shall，shouldshall用于第一、三人称的问句中时，表示征求对方的意见。如：When shall he come to meet you?他什么时候和你碰面呢？Shall we begin our class?我们可以开始上课了吗？shall用于第二、三人称的陈述句中时，表示命令、警告、允诺等。如：He shall be punished if he breaks the school rules.(警告)他如果违反校规将会被处罚。You shall stick to your post.(命令)你要坚守你的岗位。You shall have the bike if you win the game.(允诺)如果你赢了比赛你将赢得这辆自行车。should用于表示劝告和建议，作“应该”讲。如：You should keep your promise.你应该遵守诺言。should用于表示推测，表示“可能”或“应该”。如：They should be prepared now.他们现在应该准备好了。should可用于将来有可能发生某事的条件从句中，表示一件事听起来可能性小，但也不是完全不可能，相当于“万一”的意思。如：Ask Tom to ring me up if you should see him.万一你见到汤姆，叫他给我打个电话。(5) will，would表示意愿或决心。will指现在，would指过去。如：He will study harder to be a good student.他决心更努力学习来做一名好学生。They said that they would help us.他们说过愿意帮助我们。表示请求、猜想与推测。如：Will/Would you help me with my English？(请求)你能帮我学习英语吗？It would be about 8 when he left home.(推测)他回家时估计8点了。表示惯性动作，译作“总是”“惯于”。will指现在，would指过去。如：Fish will die without water.鱼没有水会死。She would sit at the table，deep in thought.过去她总是坐在桌边，陷入沉思。would可表示“过去常常”，但不涉及现在的情况；used to也表示“过去常常”，但暗示了现在不再有这个习惯。如：He used to make a lot of trouble.(现在不是了)Tom would watch TV the whole evening.(不知现在的情况)(6)ought to表示应该，否定形式为oughtnt to。如：You ought to take care of her.你应该照顾她。表示可能。如：If we start right now，we ought to be able to get there in time.如果我们现在出发，我们应该可以准时到达那。(7)need，dareneed和dare既可用作情态动词也可用作行为动词。作行为动词时，有人称和数的变化，可用于肯定句、否定句或疑问句中，构成否定句或疑问句时要用助动词do，does，did；作情态动词时，没有人称和数的变化(dare可以有过去式dared)，直接接动词原形时，只用于否定句和疑问句中，构成否定句和疑问句时不用助动词。另外，dare作情态动词时，还可用于条件句中，过去式为dared；作行为动词时，dare可用于疑问句或否定句中，后面的to也可省略；I dare say是习惯用法，意为“我想，大概”。如：He neednt do it.(情态动词)He doesnt need to do it.(行为动词)I didnt know whether he dared say that to him.(情态动词，有时态变化)He didnt dare (to) do that.(行为动词)He dared not do it.(情态动词)注意：need作行为动词时，还可表示“需要”，后接动名词的主动形式表示被动含义。如：The floor needs sweeping.这地需要打扫了。3情态动词的功能分类(1)表示能力can，could，be able to，was/were able to，could have done表示现在的或一般的能力：表示现在的或一般的能力用can或be able to (一般的能力即你无论什么时候想做就能做到的能力)；表示现在的或一般的能力时，can比be able to更普遍。如：He is a native speaker of English, so he can of course speak English quite well.(一般能力)I am starving to death.I can eat two bowls of rice now.(现在的能力)表示将来的能力，用will be able to。如：If you have a good sleep, you will be able to work out this problem.如果你睡个好觉，那么你就能解决问题。表示过去的能力。A. could，was(were) able to表示过去一般的能力。B. was (were) able to表示过去有能力并且成功地做了某事，相当于managed to do something/succeeded in doing something。C. “could have过去分词”表示过去有能力做但未做。如：She could (was able to) sing like an angel when she was a child.(过去一般的能力)The fire spread through the hotel very quickly but everyone was able to get out.(过去有能力并且成功地做了某事)I could have worked out the problem, but I didnt.(过去有能力做但未做)(2)表示推测(可能性)情态动词can可用于肯定句中表示客观的(理论的)可能性，而表示具体事情实际发生的可能性时，can一般不用于肯定句。如：Accident can happen on such rainy days.这样的多雨天气有时可能会发生事故。(客观的可能性)Peter may come with us tonight, but he isnt sure yet.彼得今晚可能来我们这儿，但他还没确定。(实际可能性，不用can)表示具体事情实际发生的可能性。A表示具体事情实际发生的可能性时，must只用于肯定句，may可用于肯定句和否定句(may not表示“可能不”)，can常用于否定句、疑问句或感叹句中，表示疑惑、惊讶或不相信等；could既可用于肯定句又可用于否定句、疑问句中。如：This cant/couldnt be done by him.这不可能是他干的。(表示不相信)This may not be done by him.这可能不是他干的。(表示不确定)He could be on his way home now.他现在可能在回家的路上了。(could不如may/might常用)Can this be done by him?这可能是他干的吗？(表示疑惑、惊讶)Mr. Bush is on time for everything. How can it be that he was late for the opening ceremony？(表示疑惑、惊讶)I didnt hear the phone. I must have been asleep.(表示肯定)Are you coming to Jeffs party?Im not sure. I might go to the concert instead.(表示不确定)Bwould，could，should，might并不一定与过去时间有关，而是表示可能性弱于它们相应的现在时形式。如：This may/might be done by him.这件事有可能是他干的。(语气依次递减)Cshould表示推测时，表示确定或可能有的未来或期望，即合乎理想的情况或结果。如：He should be around sixty years old.他可能60岁上下。(表示确定)Its nearly seven oclock. Jack should be here at any moment.(表示确定或期待)When can I come for the photos? I need them tomorrow afternoon.They should be ready by 12：00.(表示期待)(3)表示请求、允许、允诺当对方是决策者时，你代表你(们)自己(I，we)，或代表第三者(he，she，they)向对方(you)请示或提出建议时用：Shall I/we？ Shall he/she/they？ Would/Can you？ 如：Shall the driver wait outside?When shall my father be able to leave hospital?Can/Could I leave now?Would you do me a favor?could/might/would/should的委婉功能。如：Could/Might I use your bike tomorrow?Yes, you can/may.(否定：No, Im afraid not.)不可以说Yes, you could/might.回答允许时，用could/might表示委婉是不恰当的。又如：Could I borrow your dictionary?Yes, of course you can.当你自己(I)是决策者，给对方(you)或第三者(he，she，they)以命令、警告、允诺或威胁时，要用shall。此外，当宣布法律、规定时，也要用shall。如：You shall leave the room at once，and he also shall.(I order you and him to leave the room at once.)你马上给我滚出去，他也一样。(说话者的意志)It has been announced that candidates shall remain in their seats until all the papers have been collected.在所有试卷收上来之前，应试者必须坐在自己的座位上。(规则或规定)(4)表示必要性must常用来表示必要性，意为“必须”。表示现在或将来必须做某事用“must动词原形”；表示现在或将来不必做某事时，用dont have to do sth.或dont need to do sth.或neednt do sth.；表示过去没必要做某事时，分为以下情况：当表示过去没必要做某事，但事实上却做了，用neednt have done sth.；当表示过去没必要做某事，而不涉及是否做，可用didnt have to do sth.或didnt need to do sth.或It was not necessary to do sth.等。 如：You neednt have worked that late last night. It was harmful to your health.你昨晚不必工作到那么晚，那对你的身体没好处。Did you work very late last night?你昨天晚上工作到很晚吗？No，I didnt.I didnt need to work very late.不是很晚，我没必要工作到很晚。should也可以表示必要性，意为“(义务上)应该”。should表示必要性时，在语气上比must(必须)弱。“should动词原形”，表示现在或将来应该做某事(的必要性)；“shouldhave过去分词”表示过去本该做某事(的必要性)。如：I should go and visit him this afternoon, but I wonder if I will be free.今天下午我应该去看望他，但我不知道我是否有空。(表示将来的必要性)You should have come to the conference yesterday. What was the reason for your absence?你昨天应该参加那个会议。你缺席的原因是什么？(表示过去的必要性)(5)表示“宁愿做某事”时，可使用下面这些句式would rather do sth.would rather do sth. than do sth.would do sth. rather than do sth.would rather sb. did sth.(虚拟语气)prefer to do sth.prefer to do sth. rather than do sth.prefer doing sth. to doing sth.4“情态动词have done”用法一览表5.情态动词其他用法要点(1)“cannot butdo sth.”表示“不得不，只好”。如：I could not but choose to go. 我只好去。(2)cannot(或never等否定词)与enough连用表示“再也不为过”。如：I cannot thank you enough.我对你真是感激不尽。I cannot say enough in praise of his work.我对他的工作赞扬不已，怎么说也不过分。You can never be strong enough.强壮身体有百利而无一害。(3)主语通常为第二人称，口语中表不满、抱怨等情绪，must表示“偏要、硬要”做某事。如：How old are you, madam?女士，你多大年纪了？If you must know, Im twice my sons age.如果你一定想知道，我的年龄是我儿子的两倍。(4)may作“可以”讲时，其否定式是mustnt，表示“被禁止”；must作“必须”讲时，其否定式是neednt，表示“不必”。如：May I use your car?No, you mustnt.(委婉地拒绝可用：Sorry, but I am using it now.或Youd better not.等)Must I work out the problem tonight?No, you neednt.考点二：虚拟语气1非真实条件句注意：if省略时需将were/should/had提前形成倒装，特别是were倒装，仅限将来事实相反时可倒装，只倒装were，不倒装to。If I were you, I wouldnt do that.Were I you, I wouldnt do that.If you had come earlier, you would have caught the bus.Had you come earlier, you would have caught the bus.If it should rain tomorrow, I would stay at home.Should it rain tomorrow, I would stay at home.2错综时间条件句当条件状语从句表示的行为和主句表示的行为所发生的时间不一致时，被称为错综时间条件句，动词的形式要根据它所表示的时间作出相应的调整。如：If I were you, I would have gone to the theatre last night.If you had followed my advice earlier, you would be better now.3含蓄条件句(1)副词如or，otherwise意为“否则”时以及由介词with，without，but for等引出的介词短语在句中起引导条件句的作用，但它们本身并不是条件句，所以称之为含蓄条件句。有上述含蓄条件的句子往往用虚拟语气。如：He telephoned to inform me of your birthday, or I would have known nothing about it.I was ill that day. Otherwise，I would have taken part in the sports meeting.What would you do with a million dollars?Without electricity human life would be quite difficult today.But for your help, we wouldnt have finished the work so soon.(2)有些句子中，没有表示虚拟语气的词，但根据前后语意，要使用虚拟语气。如：The tree died. I should have watered it.树死了。我本应给它浇水的。You could have done better, but you didnt try your best.你本来可以做得更好，但你没有尽力。Five minutes earlier and you could have met her at the station.早来5分钟的话，你就能在车站见到她了。(3)表示希望、想法、打算、意图的动词，如intend，hope，want，plan，mean等的过去完成时态或后接不定式的完成时态时，表示与过去相反的虚拟语气。如：He had hoped for a better job，but he didnt get it.他曾希望有一份更好的工作，但他没得到。I had meant to go to the party, but I had to work extra hours to prepare a speech.我本打算去参加晚会的，但我不得不加班准备演讲。I intended to have helped you，but I was very busy at that time.我本打算帮你的，但我那时非常忙。4虚拟语气在其他从句中的应用(1)用于宾语从句中wish后面的宾语从句一般用虚拟语气，表示一种不可能实现的愿望。其谓语动词构成形式为：如：I wish (that) I were a bird and could fly freely in the sky.我希望我是一只鸟，能自由地在天空中飞。I wish (that) I had met that film star yesterday.我希望我昨天见到了那位电影明星。How I wish it werent raining now.我多希望现在没下雨啊。此外，用于If only句子How I wish that从句。如：If only I were a flying bird！How I wish I were a flying bird!If only I had seen the film！How I wish I had seen the film!用于表示建议、愿望、命令等词后的宾语从句中，常见的动词有：demand，order，require，insist，suggest，propose，advise等。宾语从句中的虚拟语气结构为“should动词原形”，should可以省略。如：He suggested that we(should) start off early the next day.他建议我们第二天早点出发。The doctor ordered that the patient (should) be sent to hospital without delay.医生吩咐，立即送病人去医院。They insisted that the boy (should) go with them.他们坚持要那个男孩和他们一起去。注意：当suggest表示“暗示，表明”，insist表示“坚持认为，强调”时，suggest/insist后的宾语从句动词已经不再后于suggest/insist所表达的动作，在这种情况下，suggest/insist后的宾语从句谓语动词不使用虚拟语气形式，应使用陈述语气形式。如：The smile on his face suggested that he was satisfied with our work.他脸上的表情表明他对我们的工作很满意。The man insisted that he had never stolen the money.那个人坚持说他没有偷钱。在would rather后的宾语从句中，也用虚拟语气，后面的动词应用过去式。如：I would rather they didnt hear of the news.我宁愿他们没有听到这个消息。(2)用于主语从句中It is desired/suggested/proposed/necessary/important/strange/natural/a pity/essentialthat从句，从句中的谓语动词用“should动词原形”，should可以省略。如：It is strange that he should have acted toward his parents like that.(act在主句谓语动词be之前时，要用“should have过去分词”)真奇怪，他竟然会那样对他父母。注意：以上句式也可以用于陈述语气。如：Its strange that he didnt come yesterday.真奇怪，他昨天没有来。Its a pity that you cant dance.真可惜，你不会跳舞。(3)用于表语从句和同位语从句中在suggestion，proposal，order，plan，idea，request，advice等名词后的表语从句和同位语从句中要用虚拟语气，其构成是“(should)动词原形”。如：My idea is that we should think it over before accepting it.我的想法是我们应该在接受他之前再三思考。We all agreed to his suggestion that we should go to Dalian for sightseeing.我们都同意我们去大连观光的建议。(4)as if/as though用在虚拟语气中如果as if引导的从句谓语动词与主句谓语动词所表达的动作同时发生，as if引导的从句谓语动词用过去式；如果as if引导的从句谓语动词所表达的动作先于主句谓语动词所表达的动作，as if引导的从句谓语动词用过去完成式；如果as if引导的从句谓语动词所表达的动作后于主句谓语动词所表达的动作，as if引导的从句谓语动词用过去将来式。如：He looks as if he were an artist.(同时)他看起来像一个演员。She speaks English so fluently as if she had studied English in America.(先于)她英语说得如此流畅好像在美国学过英语。He learns English so hard as if he would go to the USA.(后于)他如此努力地学英语好像他将要去美国。(5)虚拟语气用于定语从句中在It is(high) time(that)句型中，定语从句的谓语动词用过去式，或“should动词原形”(其中should不能省略)。此句型意为“(现在)该”，用来表示提议。如：It is(high) time that you went to school.你该上学去了。It is(high) time that we should start out.你该出发了。(6)虚拟语气用于目的状语从句中在in case，for fear that等引导的从句中，谓语动词用“(should)动词原形”。有时也用陈述语气。如：She took the raincoat with her in case/for fear that she (should) be caught in the rain.她带着雨衣以免淋雨。Youd better take an umbrella in case it rains.你最好带把雨伞以免下雨。
展开阅读全文