高三英語一輪復(fù)習(xí)（自主復(fù)習(xí)+考點演練+真題集訓(xùn)）語法篇 助動詞類 第1節(jié) 情態(tài)動詞和虛擬語氣課件

第一節(jié)情態(tài)動詞和虛擬語氣 (2) 考點一：情態(tài)動詞1情態(tài)動詞的類型和特征(1)情態(tài)動詞的類型只作情態(tài)動詞用的有：must，can(could)，may(might)，ought to?？勺髑閼B(tài)動詞也可作實義動詞的有：need，dare(美語中常用作實義動詞)?？勺髑閼B(tài)動詞也可作助動詞的有：shall(should)，will(would)。具有情態(tài)動詞的某些特征的有：have(had) to，used to。(2)情態(tài)動詞的特征有一定的詞義，但不能單獨作謂語，它們要和行為動詞或連系動詞連用，構(gòu)成謂語。適用于主語的各種人稱和數(shù)(have to例外，主語是第三人稱單數(shù)時，要用has to)。如：We/He must work hard.我們/他一定要努力工作。He has to walk home.他得步行回家。后面接動詞原形，即不帶to的不定式(ought to，have to, used to本身帶有to)。如：He may lose his way.他可能會迷路。You ought to obey the law.你要遵守法律。具有助動詞的作用，即可用來構(gòu)成否定句、疑問句及用于簡明答語。如：I cant swim. Can you swim?我不會游泳，你會游泳嗎？No, I cant either.不，我也不會。2情態(tài)動詞的基本用法及區(qū)別(1)can，could表示能力和客觀可能性。如：Some of us can use the computer now，but we couldnt last year.現(xiàn)在我們中的一些人能使用電腦了，但去年我們還不能。It will be sunny in the daytime，but it could rain later on this evening.白天會天晴，但晚上可能會下雨。表示請求和允許。如：If you keep still, you can sit on either side of the boat.如果你保持不亂動，你可以坐在船的任一邊。Can I come in?我能進來嗎？Yes, you can.是的，你可以進來。表示請求，口語中常用could代替can，使語氣更委婉，但主要用于疑問句。此類問句的答語不能用could，應(yīng)該用can。如：Could I use your bike tomorrow morning?明天上午我可以用你的自行車嗎？Yes, you can.(否定回答可用：No, Im afraid not.)是的，你可以。(不，恐怕不行。)表示驚異、懷疑(不相信)等態(tài)度，主要用于否定句、疑問句和感嘆句中。如：How can you be so foolish?你怎么這么傻呢？They cant be working at this time of day.他們不可能在這個時候工作。can和be able to都表示能力，在意義上沒有區(qū)別。但can只有現(xiàn)在時和過去時，而be able to則有更多的時態(tài)形式。在肯定句中，如果表示過去某時做成了某事，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，但每個人都成功逃出了那棟大樓。(2)may，might表示請求或允許。否定回答時，一般要用mustnt表示“禁止、阻止”之意。如：May I smoke here?我能在這抽煙嗎？Yes, please./Certainly./Yes, you may./No, you mustnt.可以，請便。/當(dāng)然可以。/是的，你可以。/不，你不能抽煙。表示可能性的推測，含有“或許”“可能”之意，用might代替may時，則語氣顯得更加不肯定。如：The news may not be true.這則新聞可能不是真的。He might have some fever.他或許發(fā)燒了。may可用來表示祝愿。如：May you be happy!祝你快樂！May you succeed!祝你成功！may as well表示“還是的好，不妨，最好，”如：You may as well tell me the truth.你不妨和我說實話。We may as well stay where we are.我們最好待在原地。(3)must，have to表示必須，其肯定回答用must，否定回答用neednt或dont have to。如：Must I finish the work today?我今天必須完成工作嗎？Yes，you must./No，you neednt./You dont have to.是的，你必須完成。/不，你需要。/你不需要。must可表示肯定性的推測，意為“一定，準(zhǔn)是”，只用于肯定句中。其否定形式為cant，表示不可能。如：You must be hungry after a long walk.走了這么遠的路你一定餓了。must表示的是說話人的主觀看法，而have to則往往強調(diào)客觀需要。如：I must go now.我現(xiàn)在必須走了。I have to go now，because my mother is in hospital.我現(xiàn)在得走了，我母親生病住院了。mustnt表示禁止、不許。如：You mustnt leave the room.你不允許離開房間。(4) shall，shouldshall用于第一、三人稱的問句中時，表示征求對方的意見。如：When shall he come to meet you?他什么時候和你碰面呢？Shall we begin our class?我們可以開始上課了嗎？shall用于第二、三人稱的陳述句中時，表示命令、警告、允諾等。如：He shall be punished if he breaks the school rules.(警告)他如果違反校規(guī)將會被處罰。You shall stick to your post.(命令)你要堅守你的崗位。You shall have the bike if you win the game.(允諾)如果你贏了比賽你將贏得這輛自行車。should用于表示勸告和建議，作“應(yīng)該”講。如：You should keep your promise.你應(yīng)該遵守諾言。should用于表示推測，表示“可能”或“應(yīng)該”。如：They should be prepared now.他們現(xiàn)在應(yīng)該準(zhǔn)備好了。should可用于將來有可能發(fā)生某事的條件從句中，表示一件事聽起來可能性小，但也不是完全不可能，相當(dāng)于“萬一”的意思。如：Ask Tom to ring me up if you should see him.萬一你見到湯姆，叫他給我打個電話。(5) will，would表示意愿或決心。will指現(xiàn)在，would指過去。如：He will study harder to be a good student.他決心更努力學(xué)習(xí)來做一名好學(xué)生。They said that they would help us.他們說過愿意幫助我們。表示請求、猜想與推測。如：Will/Would you help me with my English？(請求)你能幫我學(xué)習(xí)英語嗎？It would be about 8 when he left home.(推測)他回家時估計8點了。表示慣性動作，譯作“總是”“慣于”。will指現(xiàn)在，would指過去。如：Fish will die without water.魚沒有水會死。She would sit at the table，deep in thought.過去她總是坐在桌邊，陷入沉思。would可表示“過去常常”，但不涉及現(xiàn)在的情況；used to也表示“過去常?！?，但暗示了現(xiàn)在不再有這個習(xí)慣。如：He used to make a lot of trouble.(現(xiàn)在不是了)Tom would watch TV the whole evening.(不知現(xiàn)在的情況)(6)ought to表示應(yīng)該，否定形式為oughtnt to。如：You ought to take care of her.你應(yīng)該照顧她。表示可能。如：If we start right now，we ought to be able to get there in time.如果我們現(xiàn)在出發(fā)，我們應(yīng)該可以準(zhǔn)時到達那。(7)need，dareneed和dare既可用作情態(tài)動詞也可用作行為動詞。作行為動詞時，有人稱和數(shù)的變化，可用于肯定句、否定句或疑問句中，構(gòu)成否定句或疑問句時要用助動詞do，does，did；作情態(tài)動詞時，沒有人稱和數(shù)的變化(dare可以有過去式dared)，直接接動詞原形時，只用于否定句和疑問句中，構(gòu)成否定句和疑問句時不用助動詞。另外，dare作情態(tài)動詞時，還可用于條件句中，過去式為dared；作行為動詞時，dare可用于疑問句或否定句中，后面的to也可省略；I dare say是習(xí)慣用法，意為“我想，大概”。如：He neednt do it.(情態(tài)動詞)He doesnt need to do it.(行為動詞)I didnt know whether he dared say that to him.(情態(tài)動詞，有時態(tài)變化)He didnt dare (to) do that.(行為動詞)He dared not do it.(情態(tài)動詞)注意：need作行為動詞時，還可表示“需要”，后接動名詞的主動形式表示被動含義。如：The floor needs sweeping.這地需要打掃了。3情態(tài)動詞的功能分類(1)表示能力can，could，be able to，was/were able to，could have done表示現(xiàn)在的或一般的能力：表示現(xiàn)在的或一般的能力用can或be able to (一般的能力即你無論什么時候想做就能做到的能力)；表示現(xiàn)在的或一般的能力時，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.(現(xiàn)在的能力)表示將來的能力，用will be able to。如：If you have a good sleep, you will be able to work out this problem.如果你睡個好覺，那么你就能解決問題。表示過去的能力。A. could，was(were) able to表示過去一般的能力。B. was (were) able to表示過去有能力并且成功地做了某事，相當(dāng)于managed to do something/succeeded in doing something。C. “could have過去分詞”表示過去有能力做但未做。如：She could (was able to) sing like an angel when she was a child.(過去一般的能力)The fire spread through the hotel very quickly but everyone was able to get out.(過去有能力并且成功地做了某事)I could have worked out the problem, but I didnt.(過去有能力做但未做)(2)表示推測(可能性)情態(tài)動詞can可用于肯定句中表示客觀的(理論的)可能性，而表示具體事情實際發(fā)生的可能性時，can一般不用于肯定句。如：Accident can happen on such rainy days.這樣的多雨天氣有時可能會發(fā)生事故。(客觀的可能性)Peter may come with us tonight, but he isnt sure yet.彼得今晚可能來我們這兒，但他還沒確定。(實際可能性，不用can)表示具體事情實際發(fā)生的可能性。A表示具體事情實際發(fā)生的可能性時，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、疑問句或感嘆句中，表示疑惑、驚訝或不相信等；could既可用于肯定句又可用于否定句、疑問句中。如：This cant/couldnt be done by him.這不可能是他干的。(表示不相信)This may not be done by him.這可能不是他干的。(表示不確定)He could be on his way home now.他現(xiàn)在可能在回家的路上了。(could不如may/might常用)Can this be done by him?這可能是他干的嗎？(表示疑惑、驚訝)Mr. Bush is on time for everything. How can it be that he was late for the opening ceremony？(表示疑惑、驚訝)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.(表示不確定)Bwould，could，should，might并不一定與過去時間有關(guān)，而是表示可能性弱于它們相應(yīng)的現(xiàn)在時形式。如：This may/might be done by him.這件事有可能是他干的。(語氣依次遞減)Cshould表示推測時，表示確定或可能有的未來或期望，即合乎理想的情況或結(jié)果。如：He should be around sixty years old.他可能60歲上下。(表示確定)Its nearly seven oclock. Jack should be here at any moment.(表示確定或期待)When can I come for the photos? I need them tomorrow afternoon.They should be ready by 12：00.(表示期待)(3)表示請求、允許、允諾當(dāng)對方是決策者時，你代表你(們)自己(I，we)，或代表第三者(he，she，they)向?qū)Ψ?you)請示或提出建議時用：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.)不可以說Yes, you could/might.回答允許時，用could/might表示委婉是不恰當(dāng)?shù)?。又如：Could I borrow your dictionary?Yes, of course you can.當(dāng)你自己(I)是決策者，給對方(you)或第三者(he，she，they)以命令、警告、允諾或威脅時，要用shall。此外，當(dāng)宣布法律、規(guī)定時，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.)你馬上給我滾出去，他也一樣。(說話者的意志)It has been announced that candidates shall remain in their seats until all the papers have been collected.在所有試卷收上來之前，應(yīng)試者必須坐在自己的座位上。(規(guī)則或規(guī)定)(4)表示必要性must常用來表示必要性，意為“必須”。表示現(xiàn)在或?qū)肀仨氉瞿呈掠谩癿ust動詞原形”；表示現(xiàn)在或?qū)聿槐刈瞿呈聲r，用dont have to do sth.或dont need to do sth.或neednt do sth.；表示過去沒必要做某事時，分為以下情況：當(dāng)表示過去沒必要做某事，但事實上卻做了，用neednt have done sth.；當(dāng)表示過去沒必要做某事，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，那對你的身體沒好處。Did you work very late last night?你昨天晚上工作到很晚嗎？No，I didnt.I didnt need to work very late.不是很晚，我沒必要工作到很晚。should也可以表示必要性，意為“(義務(wù)上)應(yīng)該”。should表示必要性時，在語氣上比must(必須)弱?！皊hould動詞原形”，表示現(xiàn)在或?qū)響?yīng)該做某事(的必要性)；“shouldhave過去分詞”表示過去本該做某事(的必要性)。如：I should go and visit him this afternoon, but I wonder if I will be free.今天下午我應(yīng)該去看望他，但我不知道我是否有空。(表示將來的必要性)You should have come to the conference yesterday. What was the reason for your absence?你昨天應(yīng)該參加那個會議。你缺席的原因是什么？(表示過去的必要性)(5)表示“寧愿做某事”時，可使用下面這些句式would rather do sth.would rather do sth. than do sth.would do sth. rather than do sth.would rather sb. did sth.(虛擬語氣)prefer to do sth.prefer to do sth. rather than do sth.prefer doing sth. to doing sth.4“情態(tài)動詞have done”用法一覽表5.情態(tài)動詞其他用法要點(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等否定詞)與enough連用表示“再也不為過”。如：I cannot thank you enough.我對你真是感激不盡。I cannot say enough in praise of his work.我對他的工作贊揚不已，怎么說也不過分。You can never be strong enough.強壯身體有百利而無一害。(3)主語通常為第二人稱，口語中表不滿、抱怨等情緒，must表示“偏要、硬要”做某事。如：How old are you, madam?女士，你多大年紀(jì)了？If you must know, Im twice my sons age.如果你一定想知道，我的年齡是我兒子的兩倍。(4)may作“可以”講時，其否定式是mustnt，表示“被禁止”；must作“必須”講時，其否定式是neednt，表示“不必”。如：May I use your car?No, you mustnt.(委婉地拒絕可用：Sorry, but I am using it now.或Youd better not.等)Must I work out the problem tonight?No, you neednt.考點二：虛擬語氣1非真實條件句注意：if省略時需將were/should/had提前形成倒裝，特別是were倒裝，僅限將來事實相反時可倒裝，只倒裝were，不倒裝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錯綜時間條件句當(dāng)條件狀語從句表示的行為和主句表示的行為所發(fā)生的時間不一致時，被稱為錯綜時間條件句，動詞的形式要根據(jù)它所表示的時間作出相應(yīng)的調(diào)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含蓄條件句(1)副詞如or，otherwise意為“否則”時以及由介詞with，without，but for等引出的介詞短語在句中起引導(dǎo)條件句的作用，但它們本身并不是條件句，所以稱之為含蓄條件句。有上述含蓄條件的句子往往用虛擬語氣。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，沒有表示虛擬語氣的詞，但根據(jù)前后語意，要使用虛擬語氣。如：The tree died. I should have watered it.樹死了。我本應(yīng)給它澆水的。You could have done better, but you didnt try your best.你本來可以做得更好，但你沒有盡力。Five minutes earlier and you could have met her at the station.早來5分鐘的話，你就能在車站見到她了。(3)表示希望、想法、打算、意圖的動詞，如intend，hope，want，plan，mean等的過去完成時態(tài)或后接不定式的完成時態(tài)時，表示與過去相反的虛擬語氣。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，但他沒得到。I had meant to go to the party, but I had to work extra hours to prepare a speech.我本打算去參加晚會的，但我不得不加班準(zhǔn)備演講。I intended to have helped you，but I was very busy at that time.我本打算幫你的，但我那時非常忙。4虛擬語氣在其他從句中的應(yīng)用(1)用于賓語從句中wish后面的賓語從句一般用虛擬語氣，表示一種不可能實現(xiàn)的愿望。其謂語動詞構(gòu)成形式為：如：I wish (that) I were a bird and could fly freely in the sky.我希望我是一只鳥，能自由地在天空中飛。I wish (that) I had met that film star yesterday.我希望我昨天見到了那位電影明星。How I wish it werent raining now.我多希望現(xiàn)在沒下雨啊。此外，用于If only句子How I wish that從句。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!用于表示建議、愿望、命令等詞后的賓語從句中，常見的動詞有：demand，order，require，insist，suggest，propose，advise等。賓語從句中的虛擬語氣結(jié)構(gòu)為“should動詞原形”，should可以省略。如：He suggested that we(should) start off early the next day.他建議我們第二天早點出發(fā)。The doctor ordered that the patient (should) be sent to hospital without delay.醫(yī)生吩咐，立即送病人去醫(yī)院。They insisted that the boy (should) go with them.他們堅持要那個男孩和他們一起去。注意：當(dāng)suggest表示“暗示，表明”，insist表示“堅持認(rèn)為，強調(diào)”時，suggest/insist后的賓語從句動詞已經(jīng)不再后于suggest/insist所表達的動作，在這種情況下，suggest/insist后的賓語從句謂語動詞不使用虛擬語氣形式，應(yīng)使用陳述語氣形式。如：The smile on his face suggested that he was satisfied with our work.他臉上的表情表明他對我們的工作很滿意。The man insisted that he had never stolen the money.那個人堅持說他沒有偷錢。在would rather后的賓語從句中，也用虛擬語氣，后面的動詞應(yīng)用過去式。如：I would rather they didnt hear of the news.我寧愿他們沒有聽到這個消息。(2)用于主語從句中It is desired/suggested/proposed/necessary/important/strange/natural/a pity/essentialthat從句，從句中的謂語動詞用“should動詞原形”，should可以省略。如：It is strange that he should have acted toward his parents like that.(act在主句謂語動詞be之前時，要用“should have過去分詞”)真奇怪，他竟然會那樣對他父母。注意：以上句式也可以用于陳述語氣。如：Its strange that he didnt come yesterday.真奇怪，他昨天沒有來。Its a pity that you cant dance.真可惜，你不會跳舞。(3)用于表語從句和同位語從句中在suggestion，proposal，order，plan，idea，request，advice等名詞后的表語從句和同位語從句中要用虛擬語氣，其構(gòu)成是“(should)動詞原形”。如：My idea is that we should think it over before accepting it.我的想法是我們應(yīng)該在接受他之前再三思考。We all agreed to his suggestion that we should go to Dalian for sightseeing.我們都同意我們?nèi)ゴ筮B觀光的建議。(4)as if/as though用在虛擬語氣中如果as if引導(dǎo)的從句謂語動詞與主句謂語動詞所表達的動作同時發(fā)生，as if引導(dǎo)的從句謂語動詞用過去式；如果as if引導(dǎo)的從句謂語動詞所表達的動作先于主句謂語動詞所表達的動作，as if引導(dǎo)的從句謂語動詞用過去完成式；如果as if引導(dǎo)的從句謂語動詞所表達的動作后于主句謂語動詞所表達的動作，as if引導(dǎo)的從句謂語動詞用過去將來式。如：He looks as if he were an artist.(同時)他看起來像一個演員。She speaks English so fluently as if she had studied English in America.(先于)她英語說得如此流暢好像在美國學(xué)過英語。He learns English so hard as if he would go to the USA.(后于)他如此努力地學(xué)英語好像他將要去美國。(5)虛擬語氣用于定語從句中在It is(high) time(that)句型中，定語從句的謂語動詞用過去式，或“should動詞原形”(其中should不能省略)。此句型意為“(現(xiàn)在)該”，用來表示提議。如：It is(high) time that you went to school.你該上學(xué)去了。It is(high) time that we should start out.你該出發(fā)了。(6)虛擬語氣用于目的狀語從句中在in case，for fear that等引導(dǎo)的從句中，謂語動詞用“(should)動詞原形”。有時也用陳述語氣。如：She took the raincoat with her in case/for fear that she (should) be caught in the rain.她帶著雨衣以免淋雨。Youd better take an umbrella in case it rains.你最好帶把雨傘以免下雨。