高考二輪復習英語學案專題七 情態(tài)動詞和虛擬語氣

高考二輪復習英語教案專題七情態(tài)動詞和虛擬語氣【專題要點】情態(tài)動詞和虛擬語氣要點概覽如下：1.can和could的用法及區(qū)別；2.may和might的用法；3.must的用法；4.shall用于不同人稱時的用法；5.should表示推測時的用法；6.will和would表示意愿、習慣和傾向性時的用法；7.“情態(tài)動詞+have done”的用法；8.表示建議、命令、要求的動詞后的賓語從句中用虛擬語氣的用法；9.一些固定句式或結(jié)構(gòu)中虛擬語氣的用法；10.一些隱含、混合情況的虛擬語氣?！究季V要求】對于情態(tài)動詞考綱要求學生要掌握情態(tài)動詞的基本用法和辨析。最近幾年高考試題中常常借助語境來考查情態(tài)動詞的基本用法及其區(qū)別，因此在平時學習時準確理解和掌握情態(tài)動詞的基本用法十分重要。情態(tài)動詞的用法復雜多變，在高考試題中，命題者常常利用語境和句子之間意義上的細微差別來考查學生對情態(tài)動詞的理解和掌握。對于情態(tài)動詞，除了要求考生能夠準確掌握它們的基本用法外，還要充分利用高考試題所設(shè)置的語境來分析句子之間所體現(xiàn)的特殊關(guān)系。對于虛擬語氣考綱要求考生要掌握基本情態(tài)動詞的用法、在各種句式、隱含、混合等句中的虛擬語氣用法，根據(jù)考綱的要求，虛擬語氣部分主要考查情態(tài)動詞的選擇、虛擬語氣在條件句中、在名詞性從句中、在簡單句中或在日常交際中的使用等基本用法。因此依據(jù)語境來判斷虛擬語氣的不同形式是高考試題的主要設(shè)題方法之一。在近年的高考試題中，出現(xiàn)了對陳述語氣與虛擬語氣辨析的考查，虛擬語氣在各種從句中的應(yīng)用是該部分的重點掌握內(nèi)容。【教法指引】情態(tài)動詞是高考的重要考點，看似簡單，但用法相近、復雜，學生學起來有時區(qū)分不開。首先教師應(yīng)該讓考生準確掌握每個情態(tài)動詞的用法，然后對于相近意義的情態(tài)動詞進行比較，尤其是表示推測的一些情態(tài)動詞以及在虛擬語氣中運用，讓學生在辨析中學，在訓練中體驗、理解、掌握，要注重和語境結(jié)合和說話者的語氣結(jié)合；其次再掌握情態(tài)動詞的固定句式和固定用法即可；虛擬語氣是高考考查的重點語法項目，雖然不是每套題都涉及，但在近幾年的考題中也有不少出現(xiàn)。由于漢語中沒有這種語法情況，對于以漢語為母語的我們來說有很大的理解難度。命題者在試題的有效信息方面越來越隱蔽，情景越來越生動，真實，考查的角度也越來越靈活。要掌握好這一語法項目，要求考生：1. 熟記并掌握虛擬語氣在非真實條件句中的使用規(guī)則；2. 熟練掌握虛擬語氣在名詞性從句中的使用；3. 掌握一些特殊句型中要運用虛擬語氣的具體規(guī)則。【知識網(wǎng)絡(luò)】情態(tài)動詞的用法   情態(tài)動詞表示說話人對某一動作或狀態(tài)的態(tài)度，可以表示“可能”、“可以”、“需要”、“必須”或“應(yīng)當”等之意。情態(tài)動詞沒有人稱和數(shù)的變化。但不能單獨作謂語動詞用，必須和不帶to的不定式連用構(gòu)成謂語動詞。只有情態(tài)動詞ought要和帶to的動詞不定式連用，在句中作謂語用。將情態(tài)動詞置于主語之前即構(gòu)成其疑問式，在情態(tài)動詞之后加not既構(gòu)成其否定式。現(xiàn)將各情態(tài)動詞的基本用法分述如下： 1、can和could (could為can的過去式) 的基本用法(1)表示能力，如：He can speak English better than you. (2)在疑問句和否定句中表示“懷疑”、“猜測”或“可能性”，如：Can this green bike be Liu Dong's?(3)表示“許可”時can可以和may換用，如：You can (may) go home now. (4)如果要表示語氣婉轉(zhuǎn)，可用could代替can，這時could不再是can的過去式，如：Could you come again tomorrow? (5)can和be able to都可表示能力，兩者在意思上沒有什么區(qū)別。但是can只能有現(xiàn)在式和過去式，而be able to則有更多的形式，如：He will be able to do the work better.2、may和might (might為may的過去式)的基本用法(1)表示允許或征詢對方許可，有“可以”之意，如：You may use my dictionary. 在回答對方說“可以做某事”或“不可以做某事”時，一般多不用may或 may not，以避免語氣生硬或不容氣。而用比較婉轉(zhuǎn)的說法進行回答。如：- May I use this dictionary? - Yes, please. 或 - Certainly. 在請求對方許可時，如果Might I? 就比用May I? 語氣更婉轉(zhuǎn)些，如：May I have a look at your new computer? 但是表示“阻止”或“禁止”對方做某事時，要用must not代替may not，如：- May we swim in this lake? - No, you mustnt. Its too dangerous.(2)may或 might都可以表示可能性，表示“或許”、“可能”之意，如果用might表示可能性，則語氣更加不肯定，如：They may (might) be in the library now .3、must的基本用法(1)must表示“必須”、“應(yīng)該”之意，其否定式 must not，縮寫形式為 mustn't，表示“不應(yīng)該”，“不準”、“不許可”或“禁止”之意，如：We must study hard and make progress every day. You mustn't touch the fire. (2)對以must提出的疑問句，如作否定回答時，要用needn't或用don't (doesn't) have to (不必)來回答，而不用mustn't，因為mustn't表示的是“禁止”或“不許可”之意，如：- Must we finish the work tomorrow? - No, you needn't (don't have to), but you must finish   it in three days. (3)在肯定句中must可以表示推測，表示“一定”或“必定”之意，如：- Whose new bike can it be? - It must be Liu Dong's. I know his father has just bought him a new one.4、can, could, may, must后接完成式的用法(1)can, could后接完成式的用法：在否定句或疑問句中表示對過去發(fā)生過的事情的“懷疑”或“不肯定”的態(tài)度，Could he have said so? 在肯定句中，可以表示過去可能做到而實際并沒做到的事情，有“勸告”或“責備”的語氣。如：- When did you answer her letter? - Only yesterday. - It's too late. You could have answered it earlier, I am sure. (2)may, might后接完成式的用法表示對過去某事的推測，認為某一件事情在過去可能發(fā)生了。如果使用might，語氣就比較婉轉(zhuǎn)或更加不肯定，如：Mary might have learned some Chinese before. 可以表示過去本來可以做到而實際沒有做到的事情，有“勸告”或“責備”的語氣，如：You didn't do the work well that day. You might have done it better. (3)must后接完成式的用法：表示對過去某事的推測，認為某事在過去一定做到了，如：Liu Dong isnt in the classroom. He must have gone to the library. 5、have to 的基本用法：have to和must的意義相近，只是 must側(cè)重表示說話人的主觀看法，而have to 則表示客觀需要，如：I must study hard. I had to give it up because of illness.                                                6、ought to的基本用法(l)表示根據(jù)某種義務(wù)或必要“應(yīng)當”做某事，語氣比should強，例如：Everyone ought to obey the traffic regulations. (2)表示推測，注意與must表示推測時的區(qū)別：He must be home by now .(斷定他已到家)，He ought to be home by now .(不十分肯定)，This is where the oil must be.(比較直率) ，This is where the oil ought to be. (比較含蓄) ；(3)“ought + have+ 過去分詞”表示過去應(yīng)做某事而實際未做。例如：You ought to have helped him. (but you didnt) 這時，ought與 should可以互相換用。注意，在美國英語中ought to 用于否定和疑問句時to可以省略。例如：Ought you smoke so much? You oughtnt smoke so much.7、dare的基本用法(l)dare (dared為其過去式) 作情態(tài)動詞用時，主要用于否定句，疑問句和條件從句中，如：Dared he bread the traffic regulations again? (2)在現(xiàn)代英語中dare常用作行為動詞，其變化與一般行為動詞相同，如：She dares to stay at home alone at night.8、need的基本用法(1)need作情態(tài)動詞用時，主要用于否定句和疑問句中，如：He needn't worry about us now. (2)need也可作為行為動詞用，可用于肯定句，否定句和疑問句中，其后可接名詞、代詞、動名詞或帶 to 的動詞不定式為其賓語。如：You need to practise reading aloud every day. (3)needn't后接完成式可以表示過去做了一件本來不必要做的事情，如：- Did you answer the letter yesterday? - Yes, I did. - But you neednt have answered it.9、shall的基本用法(1)shall用作情態(tài)動詞時，用于第二、三人稱，表示說活人的意愿，可表示“命令”、“警告”、“強制”、“威脅”或“允諾”等意，如：He shall go first, whether he wants to or not. (2)在疑問句中，shall用于第一、三人稱，表示說話人的征詢對方意見或請求指示，如：Shall I open the door?10、should的基本用法(1)should作為情態(tài)動詞可以表示“建議”或“勸告”，有“應(yīng)該”之意，如：You should learn from each other. (2)should后接完成式表示過去沒有做到本來應(yīng)該做的事情，或是做了本來不應(yīng)該做的事情。如：You should have give him more help. 11、will的基本用法(1)用于各人稱，可以表示“意志”或“決心”，如：I have told him again and again to stop smoking, but he will not listen. (2)在疑問句中用于第二人稱，表示說話人向?qū)Ψ教岢稣埱蠡蛟儐枌Ψ降囊庠?，如：Will you please tell me how to get to the Capital Gymnasium? (3)will可以表示一種習慣性的動作，有“總是”或“會要”之意，如：Every morning he will have a walk along this river.12、would的基本用法(1)would作為will的過去式，可用于各人稱，表示過去時間的“意志”或“決心”，如：He promised he would never smoke again.(2)在疑問句中，用于第二人稱，表示說話人向?qū)Ψ教岢稣埱蠡蛟S問對方的意愿時，比用will的氣更加婉轉(zhuǎn)，如：Would you like some more coffee? (3)在日常生活中，學用“I would like to”表示“我想要”或“我愿意”之意，以使語氣婉轉(zhuǎn)，如：I would like to do Ex.2 first.(4)would可以表示過去的習慣動作，比used to正式，并沒有“現(xiàn)已無此習慣”的含義。如：Last year our English teacher would sometimes tell us stories in English after class. / During the vacation he would visit me every week. (5)表料想或猜想，如：It would be about ten when he left home./ What would she be doing there?/ I thought he would have told you about it.13、used to, had better, would rather的用法(1)used to表示過去的習慣動作或狀態(tài)，現(xiàn)在已不存在，在間接引語中，其形式可不變，例如：He told us he used to play foot ball when he was young. 在疑問句、否定句、否定疑問句或強調(diào)句中，可有兩種形式。疑問句：Did you use to/ Used you to go to the same school as your brother? 否定句：I usednt to / didnt use to go there. (usednt 也可寫作usent)；否定疑問句：Usent you to/ Didnt you use to be interested in the theatre? 強調(diào)句：I certainly used to/ did use to smoke, but it was a long time ago.；其反意疑問句或簡略回答中，也有兩種形式：She used to be very fat. didnt she?/ use(d)nt she? Did you use to play chess? Yes, I did./ Used you to get up early in the morning? Yes, I did./ used to.(2)had better意為“最好”，后接不帶to的不定式，例如：- We had better go now . - Yes, we had (we'd better/ we had better)./ Hadnt we better stop now? (Had we better not stop now?)/ I think Id better be going. (用于進行時態(tài)，表“最好立即”)/ You had better have done that (用于完成時態(tài)，表未完成動作) 注：had better用于同輩或小輩，對長輩不可用。(3)would rather意為“寧愿”，表選擇，后接不帶to的不定式，例如：Id rather not say anything./ Would you rather work on a farm?/ - Wouldnt you rather stay here? - No, I would not. Id rather go there. 由于would rather表選擇，因而后可接than，例如：I would rather work on a farm than in a factory. / I would rather watch TV than go to see the film/ I would rather lose a dozen cherry trees than that you should tell me one lie./ Id rather you didnt talk about this to anyone. (句中的 'd rather不是情態(tài)動詞，would 在此是表愿望的實義動詞)。虛擬語氣的用法一、語氣的種類：英語句子中謂語動詞的語氣有四種：1. 直陳語氣（The Indicative Mood）直陳語氣用于直截了當?shù)仃愂鍪聦?、描述狀態(tài)：He has published quite a number of essays this year .他今年已發(fā)表了好幾篇論文。2. 祈使語氣（The Imperative Mood）祈使語氣用于提出請求、命令、建議或是勸告等：Wait outside until you are asked . 請在外面等候，請你進再進去。Let's just take a break, shall we ? 我們休息一會兒，好嗎？3. 疑問語氣( the interrogative mood ) ：用來提出問題Where are from ?4. 虛擬語氣（The Subjunctive Mood）虛擬語氣用于表示主觀愿望和假設(shè)的虛擬情況。虛擬語氣不太顧及事實的存在，它表現(xiàn)出說話人的主觀因素比較多。所以說話人所講的內(nèi)容往往是與事實相反的；或是其實現(xiàn)的可能性微乎其微，甚至于沒有實現(xiàn)的可能性。當然，有時為了使說話的語氣客氣、緩和、委婉，也使用虛擬語氣。I wish you were more careful .但愿你更細心一些。If I had more money, I would buy a bigger apartment.我要是有再多一點錢，我就買一套更大一些房子。Would you mind shutting the door ? 勞駕您把門關(guān)上。二、虛擬語氣的種類：虛擬語氣用來表示說話人的主觀愿望或假想，所說的是一個條件，不一定是事實，或與事實相反。虛擬語氣在條件句中應(yīng)用比較多；條件句可分為兩類，一類為真實條件句，一類為非真實條件句。非真實條件句表示的是假設(shè)的或?qū)嶋H可能性不大的情況，故采用虛擬語氣。三、真實性條件句1.真實條件句用于陳述語氣，假設(shè)的情況有可能發(fā)生,各種結(jié)構(gòu)如下：條件從句          主句一般現(xiàn)在時    shall/will + 動詞原形祈使句        情態(tài)動詞一般現(xiàn)在時If he comes, he will bring his violin. 如果他來，會帶小提琴來的。【典型例題】The volleyball match will be put off if it_.A.will rain B. rains C. rained D. is rained【解析】B 真實條件句主句為將來時，從句用一般現(xiàn)在時。【點撥】1. 在真實條件句中，主句不能用be going to表示將來，該用shall, will.（錯） If you leave now, you are never going to regret it.（對） If you leave now, you will never regret it.2. 表示真理時，主句謂語動詞不用shall （will） +動詞原形，而直接用一般現(xiàn)在時的動詞形式四、非真實條件句1. 虛擬語氣可以表示過去，現(xiàn)在和將來的情況，時態(tài)的基本特點是時態(tài)往后推移2. 虛擬語氣表時間從句主句例句與現(xiàn)在事實相反的假設(shè)一般過去時（ be 用were）Would / should / could / might / ought to  + 動詞原形1. If they were here, they would help you.2. If we had enough money , we would buy a computer .3. If I were you , I wouldnt do it .4. If it rained tomorrow , wed stay at home .5. It would be odd if she were awarded the first prize .與過去事實相反的假設(shè)過去完成時Should / would / could / might + have+ 過去分詞1. If he had come yesterday, I should have told him about it.2.If I had been in her position Id have quit .3. If the weather hadnt been so bad , we might have gone out .4. If he had apologized , you should have done so too.5. I should never have done it if I hadnt been so hard up .與將來不大可能發(fā)生的事情的假想一般過去時 / should/would  + 動詞原形Should / would  / could / might / ought to + 動詞原形1. If you succeeded, everything would be all right.2. If they invited me , I would certainly attend it .3. If he went , would you go too ?與將來事實相反的假設(shè)were+ 不定式Should / would  / could / might / ought to + 動詞原形1. If she were to lose her place they would be ruined .2.If you were to speak to him , it would carry more weight .五、混合條件句(也叫：錯綜時間條件句)有時，主句與從句的動作發(fā)生在不同的時間，主句從句謂語動詞的虛擬語氣形式因時間不同而不同，這種條件句叫做混合條件句If you had asked him yesterday, you would know what to do now. 如果你昨天問過他，今天就知道做什么了。（從句與過去事實相反，主句與現(xiàn)在事實相反。）1. If it had rained last night（過去）, it would be very cold today （現(xiàn)在）.如果昨晚下過雨，今天就會很冷了。2. If youd listened to me , you wouldnt be in such trouble now . 如果你聽了我的話，你現(xiàn)在也不會這樣麻煩了3. If it hadnt been for her care , I should not be speaking to you now. 如果不是她照顧我，我也不會在這里和你講話4. If the doctor had come in time , any would still be alive . 如果醫(yī)生及時趕到，AMY現(xiàn)在還活著。六、含蓄條件句：含蓄條件句是指非真實條件句中的條件從句有時不表出來,只暗含在上下文中。含蓄條件句常見的表達方式有:1. 定語從句和狀語從句Anyone who had married such a girl as she would have been regretful . 誰娶了像她這樣的姑娘都會后悔的help was promised where it should become necessary . 要是需要的話就答應(yīng)給予幫助2. 介詞及介詞短語but that, as though, once ,but for, without , with , under , undercondition , supposing , suppose , as if , on condition that , in the past 等But for his pension , he would starve .要不是有養(yǎng)老金，他都要餓死了Without your help , I couldnt have achieved all this . 要不是有你幫助我不會取得這些成就With his aid , you would succeed . 如果有了他的幫助，你就會成功。Plants would die without water on the earth . 地球上如果沒有水，植物就會死的But for the fog we would have reached our destination long ago . 要是沒有霧的話，我們很早就到目的地了Under more favourable conditions we could have finished the task . 如果條件對我們更有利，我們就會把工作完成得更好3. 連詞otherwise, or, butHe would have given you more help , but he has been so busy . 他本來要多給你一些幫助，只是他太忙了Seize the chance , otherwise you would regret it . 如果不抓住這個機會，你會后悔的He felt very tired yesterday , or he would have helped you . 他昨天覺得很累，不然會幫你的4. 通過分詞短語表示條件Given more time, we could have done it better.Legalizing this drug would have disastrous consequence . 使毒品合法化會有災難性的后果5. 用動詞不定式表示條件It would be a mistake not to help him.She would have done anything to make amends . 她會做任何事來彌補特殊情況：情態(tài)動詞在日常用語中用得很多，使句子顯得比較委婉；這類謂語算不算虛擬語氣很難說，但有兩點是肯定的：一是它們不受時態(tài)的影響，雖然形式接近過去式，卻常指現(xiàn)在的情況，而且和虛擬語氣在形式上一致，在不少情況下幾乎可以說是一種含蓄的虛擬條件句；二是它們不表示事實，常帶有主觀色彩，因而使句子顯得很委婉。I should think that might be a good solution .could I trouble you with a question ?could you lend me some money ?would you mind taking part ?would you like some tea ?七、虛擬語氣在賓語從句中的運用1.  虛擬語氣用在would rather，would（just）as soon，would sooner，would prefer（希望）等后接的賓語從句中。意指某人寧愿讓另一個人做某事，其后的賓語從句的謂語動詞需用虛擬語氣。若表示現(xiàn)在或?qū)硪瞿呈?，從句謂語動詞需用一般過去時，表示過去已經(jīng)做的事，從句謂語動詞用過去完成時。The manager would rather his daughter did not work in the same office經(jīng)理寧愿她女兒不與他在同一間辦公室工作。To be frank，I'd rather you were not involved in the case坦率地說，我希望你不要卷入這件事。You don't have to be in such a hurryI would rather you went on business first你沒有必要這么著急，我寧愿你先去上班。I'd rather you didn't make any comment on the issue for the time being我倒希望你暫時先不要就此事發(fā)表意見。Frankly speaking ，I'd rather you didn't do anything about it for the time being坦白地說我寧愿你現(xiàn)在對此事什么也不做。Wouldn't you rather your child went to bed early？為什么你不愿讓你的孩子早點上床呢？【點撥】若某人愿自己做某事， would rather后用動詞原形   I would rather stay at home today would ratherthan中用動詞原形            I would rather stay at home than go out today2. 在表示命令、建議、要求等一類動詞后面的從句中，像order, suggest, propose, require, demand, request, insist, command,insist + （should） doI suggest that we （should） hold a meeting next week. 我建議下周召開個會議。He insisted that he （should ） be sent there.他要求被派到那兒去?！军c撥】如suggest, insist不表示"建議" 或"堅持要某人做某事時"，即它們用于其本意"暗示、表明"、"堅持認為"時，賓語從句用陳述語氣。判斷改錯：  （錯） You pale face suggests that you（should）be ill.（對） Your pale face suggests that you are ill.（錯） I insisted that you（should）be wrong.（對） I insisted that you were wrong.3.  wish的用法1）wish后面的從句，表示與事實相反的情況，或表示將來不太可能實現(xiàn)的愿望時，其賓語從句的動詞形式為：              主句  從句從句動作先于主句動詞動作（be的過去式為 were）          現(xiàn)在時            過去時從句動作與主句動作同時發(fā)生（had + 過去分詞）           過去時/現(xiàn)在時   過去完成時將來不大可能實現(xiàn)的愿望                    將來時/現(xiàn)在時     would/could +動詞原形I wish I were as tall as you.我希望和你一樣高He wished he hadn't said that. 他希望他沒講過那樣的話I wish it would rain tomorrow. 我希望明天下雨就好了I wish that he werent so lazy . 但愿他不那么懶He wishes that he were a teacher .  他希望他是個老師就好了I wish that he had not made so much fuss about it . 但愿那時他對這事不那么大驚小怪I wish that the rain would stop . 要是雨停就好了2）在“it is wished that”句型以及作名詞所引起的表語和同位語從句中也要求使用虛擬語氣，用法同上。3)  wish to do；wish sb / sth to doI wish to see the manager. = I want to see the manager. 我希望見一見經(jīng)理。I wish the manager to be informed at once. （= I want the manager to be informed at once.）我希望經(jīng)理能馬上得到消息八、虛擬語氣用在表語從句或同位語從句中當某些表示建議、請求、命令等主觀意向的名詞作主語時，其后的表語從句或同位語從句需用虛擬語氣，其表達形式為should 動詞原形或直接用動詞原形。這類名詞常見的有：advice，suggestion，proposal，order， demand，desire，request，requirement，recommendation , aim , wish , necessity , preference , motion , plan，idea，resolution等。We are all for your proposal that the discussion be put off我們都贊成你提出的將討論延期的建議。The suggestion that the mayor present the prizes was accepted by everyone由市長頒發(fā)獎金的建議被每個人接受。Any proposals that john should be dismissed must be resisted . 必須抵制任何開除JOHN的提議His idea that we should take up the matter with a special board is fairly resonable . 他建議我們以一個專門委員會處理這件事，這的確有道理Our suggestion is that we should put on a play at the english evening . 我們建議在英語晚會上演一個劇九、 在主語從句中的應(yīng)用It is / was  + necessary + that + 主語 + should + 加動詞原形，should 可省略，表示建議、命令、請求、道歉、懷疑、驚奇等可用的詞有：suggested, ordered, required, proposed, demanded , requested, insisted , important, necessary, natural, imperative, strange , a pity, a shame, no wonder , essential , advisable , mandatory , obligatory , vital , compulsory , crucial , fitting , better , best , appropriate , recommended 十、虛擬語氣在其他狀語從句中的使用1.  虛擬語氣用在目的狀語從句中在由lest , for fear that , in order that , so that , in case of 等引導的目的狀語從句中需用虛擬語氣，表示“以防，以免”等意思，其謂語動詞多由should / could / might + 動詞原形構(gòu)成，should也可省略。He was punished lest he should make the same mistake again他被處以懲罰以免他再犯。I reminded her twice of it lest she should forget . 我提醒她兩次，怕她忘記I will not make a noise for fear that I should disturb him . 我不會出聲的，以免打擾他I have come all the way here in order that you should understand me . 我到這里來為的是你能理解我He put his coat over his son in case he should catch cold . 他把大衣蓋在兒子身上以免他著涼注意：如果 in order that 和 so that 前的主句是現(xiàn)在時，其后的從句有時也可用 can , may + 動詞原形。Ask him to hurry up with the letters so that I can sign them . 讓他帶著信趕快來以便我簽字在以lest 和in case 引導的目的狀語從句中謂語動詞若屬于過去時，一般要用虛擬語氣， should + 動詞原形，若謂語動詞不是過去時，也可以用成述語氣。take warm clothes in case the weather is cold . 帶上厚衣服以防天變冷。2. 虛擬語氣在方式狀語從句中在as if（as though）引導的方式狀語從句中，常用虛擬語氣，表示似乎，好象的意思，其動詞形式與wish后接賓語從句中的形式相同。Alan talked about Rome as if he were a Roman艾倫談起羅馬來好像他是個羅馬人一樣。I feel as if I were ten years younger . 我覺得我仿佛年輕了10歲He talks about pyramids as though he had seen them himself . 他談起金字塔來，就好象親眼見過似的I feel as if we had known each other for years . 我感到我們好象已經(jīng)認識多年了It looks as if it might rain . 看上去好象要下雨十一、虛擬語氣的倒裝形式在書面語中，如果條件從句含有 were, had, should，可將連詞 if 省略，再將 were, had 或 should 移至句首，構(gòu)成非真實條件句的倒裝語序Were they here now, they could help us. =If they were here now, they could help us.他們現(xiàn)在在的話，就會幫助我們了。Had you come earlier, you would have met him. =If you had come earlier, you would have met him.你來得早一點，就碰到他了。Should it rain, the crops would be saved. =Were it to rain, the crops would be saved.假如下雨，莊稼就有救了。【典型例題】_ to do the work, I should do it some other day.    A. If were I B. I were C. Were I D. Was I答案C. 在虛擬條件狀語中如果有were, should, had這三個詞，通常將if省略，主語提前, 變成 were, should, had +主語的形式。但要注意，在虛擬條件狀語從句中，省略連詞的倒裝形式的句首不能用動詞的縮略形式。如我們可說Were I not to do, 而不能說 Weren't I to do.e.g.  Had you been here just now, you would have met her. 你要是剛才在這兒，就見到她了。Were I not busy, I would have come. 假如我不忙，我就會來了。十二、其他句型1. 虛擬語氣用在It is 形容詞that的主語從句中在某些表示愿望、建議、請求、命令等形容詞后的主語從句中，需用虛擬語氣。其表達形式為should 動詞原形或省略should直接用動詞原形。這類形容詞有 advisable（合理的），appropriate（適當?shù)模?，compulsory（必須的），crucial（緊急的），desirable（理想的），essential（必要的），imperative（迫切的），important（重要的），incredible（驚人的），natural（自然的），necessary（必要的），possible（可能的），preferable（更好的）， probable（可能的），strange（奇怪的），urgent（緊迫的）， vital（極為重要的）。It is essential that these application forms be sent back as early as possible這些申請表應(yīng)盡早地寄回，這是很重要的。It is vital that enough money be collected to fund the project重要的是募集足夠的錢，為這個項目提供資金。2. 虛擬語氣用在It is 過去分詞that的主語從句中在It is 過去分詞that的主語從句中，常用虛擬語氣，表示愿望、建議、請求等主觀意向，謂語用 should 動詞原形或省略should只用動詞原形。這類過去分詞有：decided，demanded，desired，insisted，ordered，proposed，suggested，recommended，requested， required等。It is desired that we（should）get everything ready this evening希望我們今晚一切都準備就緒。3. 虛擬語氣用在It is（about high）time that定語從句中在It is（abouthigh）time that定語從句中需用虛擬語氣，表示“該做的時候了”，其動詞形式用一般過去時或should 動詞原形It's already 5 o'clock now,Don't you think it's about time we went home？已經(jīng)5點鐘了，你不認為我們應(yīng)該回家了嗎？【點撥】在this is the first time second time that句型中，從句中謂語動詞用陳述語氣完成時態(tài)Is this the first time that you have visited Hongkong？這是你第一次參觀香港嗎？It's time to do something有別于It's time that4. 比較if only與only ifonly if表示"只有"；if only則表示"如果就好了"。If only引起的句子，一般過去時或would+動詞原形表示現(xiàn)在或未來事實相反，過去完成時表示與過去事實相反，也可用于陳述語氣I wake up only if the alarm clock rings. 只有鬧鐘響了，我才會醒。If only the alarm clock had rung.當時鬧鐘響就好了。If only he comes early.但愿他早點回來If only we knew where to look for him. 我們要是知道到哪里去找他就好了If only I had listened to my parents.   要是我聽取了父母的話該多好啊5. but 或 but that 表達的含蓄條件的特殊含義but 或 but that 做“如果不”解，意思相當與“if not”，其后面不可接虛擬模式，應(yīng)接陳述式的現(xiàn)在時動詞或過去時動詞，即but that + 主語 + 現(xiàn)在時動詞 / 過去式動詞，而主句要用虛擬式。But that you help him , he would fail . 如果沒有你的幫助，他會失敗的But that you helped him , he would have failed . 如果沒有你的幫助，他早就失敗了6.  need “不必做”和“本不必做”didn't need to do表示過去不必做某事, 事實上也沒做；needn't have done表示過去不必做某事, 但事實上做了John went to the station with the car to meet Mary, so she didn't need to walk back home.約翰開車去車站接瑪麗，所以她不必步行回家了John went to the station with the car to meet Mary, so she needn't have walked back home.約翰開車去車站接瑪麗，所以她本不必步行回家了。（Mary步行回家了，沒有遇上John的車）【典型例題】There was plenty of time. She _.A. mustn't have hurried B. couldn't have hurriedC. must not hurry D. needn't have hurried【解析】 D needn't have done. 意為"本不必"，即已經(jīng)做了某事，而時實際上不必要。Mustn't have done 用法不正確，對過去發(fā)生的事情進行否定性推斷應(yīng)為couldn't have done, "不可能已經(jīng)"。must not do 不可以（用于一般現(xiàn)在時）7. 不定式的完成時用在 intend , mean , plan , suppose 等動詞后，表示原打算做而實際未能做而實際未能做成的事，因而含有虛擬的意思8.  need / need