2019-2020年高考英语二轮 情态动词和虚拟语气1.doc

2019-2020年高考英语二轮 情态动词和虚拟语气1【专题要点】情态动词和虚拟语气要点概览如下：1.can和could的用法及区别；2.may和might的用法；3.must的用法；4.shall用于不同人称时的用法；5.should表示推测时的用法；6.will和would表示意愿、习惯和倾向性时的用法；7.“情态动词+have done”的用法；8.表示建议、命令、要求的动词后的宾语从句中用虚拟语气的用法；9.一些固定句式或结构中虚拟语气的用法；10.一些隐含、混合情况的虚拟语气。【考纲要求】对于情态动词考纲要求学生要掌握情态动词的基本用法和辨析。最近几年高考试题中常常借助语境来考查情态动词的基本用法及其区别，因此在平时学习时准确理解和掌握情态动词的基本用法十分重要。情态动词的用法复杂多变，在高考试题中，常常利用语境和句子之间意义上的细微差别来考查学生对情态动词的理解和掌握。对于情态动词，除了要求考生能够准确掌握它们的基本用法外，还要充分利用高考试题所设置的语境来分析句子之间所体现的特殊关系。对于虚拟语气考纲要求考生要掌握基本情态动词的用法、在各种句式、隐含、混合等句中的虚拟语气用法，根据考纲的要求，虚拟语气部分主要考查情态动词的选择、虚拟语气在条件句中、在名词性从句中、在简单句中或在日常交际中的使用等基本用法。因此依据语境来判断虚拟语气的不同形式是高考试题的主要设题方法之一。在近年的高考试题中，出现了对陈述语气与虚拟语气辨析的考查，虚拟语气在各种从句中的应用是该部分的重点掌握内容。【教法指引】情态动词是高考的重要考点，看似简单，但用法相近、复杂，学生学起来有时区分不开。首先教师应该让考生准确掌握每个情态动词的用法，然后对于相近意义的情态动词进行比较，尤其是表示推测的一些情态动词以及在虚拟语气中运用，让学生在辨析中学，在训练中体验、理解、掌握，要注重和语境结合和说话者的语气结合；其次再掌握情态动词的固定句式和固定用法即可；虚拟语气是高考考查的重点语法项目，虽然不是每套题都涉及，但在近几年的考题中也有不少出现。由于汉语中没有这种语法情况，对于以汉语为母语的我们来说有很大的理解难度。在试题的有效信息方面越来越隐蔽，情景越来越生动，真实，考查的角度也越来越灵活。要掌握好这一语法项目，要求考生：1. 熟记并掌握虚拟语气在非真实条件句中的使用规则；2. 熟练掌握虚拟语气在名词性从句中的使用；3. 掌握一些特殊句型中要运用虚拟语气的具体规则。【知识网络】 情态动词的用法 情态动词表示说话人对某一动作或状态的态度，可以表示“可能”、“可以”、“需要”、“必须”或“应当”等之意。情态动词没有人称和数的变化。但不能单独作谓语动词用，必须和不带to的不定式连用构成谓语动词。只有情态动词ought要和带to的动词不定式连用，在句中作谓语用。将情态动词置于主语之前即构成其疑问式，在情态动词之后加not既构成其否定式。现将各情态动词的基本用法分述如下： 1、can和could (could为can的过去式) 的基本用法(1)表示能力，如：He can speak English better than you. (2)在疑问句和否定句中表示“怀疑”、“猜测”或“可能性”，如：Can this green bike be Liu Dongs?(3)表示“许可”时can可以和may换用，如：You can (may) go home now. (4)如果要表示语气婉转，可用could代替can，这时could不再是can的过去式，如：Could you e again tomorrow? (5)can和be able to都可表示能力，两者在意思上没有什么区别。但是can只能有现在式和过去式，而be able to则有更多的形式，如：He will be able to do the work better.2、may和might (might为may的过去式)的基本用法(1)表示允许或征询对方许可，有“可以”之意，如：You may use my dictionary. 在回答对方说“可以做某事”或“不可以做某事”时，一般多不用may或 may not，以避免语气生硬或不容气。而用比较婉转的说法进行回答。如：- May I use this dictionary? - Yes, please. 或 - Certainly. 在请求对方许可时，如果Might I? 就比用May I? 语气更婉转些，如：May I have a look at your new puter? 但是表示“阻止”或“禁止”对方做某事时，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“或许”、“可能”之意，如果用might表示可能性，则语气更加不肯定，如：They may (might) be in the library now .3、must的基本用法(1)must表示“必须”、“应该”之意，其否定式 must not，缩写形式为 mustnt，表示“不应该”，“不准”、“不许可”或“禁止”之意，如：We must study hard and make progress every day. You mustnt touch the fire. (2)对以must提出的疑问句，如作否定回答时，要用neednt或用dont (doesnt) have to (不 必)来回答，而不用mustnt，因为mustnt表示的是“禁止”或“不许可”之意，如：- Must we finish the work tomorrow? - No, you neednt (dont have to), but you must finish it in three days. (3)在肯定句中must可以表示推测，表示“一定”或“必定”之意，如：- Whose new bike can it be? - It must be Liu Dongs. 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：在否定句或疑问句中表示对过去发生过的事情的“怀疑”或“不肯定”的态度，Could he have said so? 在肯定句中，可以表示过去可能做到而实际并没做到的事情，有“劝告”或“责备”的语气。如：- When did you answer her letter? - Only yesterday. - Its too late. You could have answered it earlier, I am sure. (2)may, might后接完成式的用法 表示对过去某事的推测，认为某一件事情在过去可能发生了。如果使用might，语气就比较婉转或更加不肯定，如：Mary might have learned some Chinese before. 可以表示过去本来可以做到而实 际没有做到的事情，有“劝告”或“责备”的语气，如：You didnt do the work well that day. You might have done it better. (3)must后接完成式的用法：表示对过去某事的推测，认为某事在过去一定做到 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的意义相近，只是 must侧重表示说话人的主观看法，而have to 则表示客观需要，如：I must study hard. I had to give it up because of illness. 6、ought to的基本用法(l)表示根据某种义务或必要“应当”做某事，语气比should强，例如：Everyone ought to obey the traffic regulations. (2)表示推测，注意与must表示推测时的区别：He must be home by now .(断定他已到家)，He ought to be home by now .(不十分肯定)，This is where the oil must be.(比较直率) ，This is where the oil ought to be. (比较含蓄) ；(3)“ought + have+ 过去分词”表示过去应做某事而 实际未做。例如：You ought to have helped him. (but you didnt) 这时，ought与 should可以互相换用。注意，在美国英语ought to 用于否定和疑问句时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为其过去式) 作情态动词用时，主要用于否定句，疑问句和条件从句中，如：Dared he bread the traffic regulations again? (2)在现代英语中dare常用作行为动词，其变化与一般行为动词相同，如：She dares to stay at home alone at night.8、need的基本用法(1)need作情态动词用时，主要用于否定句和疑问句中，如：He neednt worry about us now. (2)need也可作为行为动词用，可用于肯定句，否定句和疑问句中，其后可接名词、代词、动名词或带 to 的动词不定式为其宾语。如：You need to practise reading aloud every day. (3)neednt后接完成式可以表示过去做了一件本来不必要做的事情，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用作情态动词时，用于第二、三人称，表示说活人的意愿，可表示“命令”、“警告”、“强制”、“威胁”或“允诺”等意，如：He shall go first, whether he wants to or not. (2)在疑问句中，shall用于第一、三人称，表示说话人的征询对方意见或请求指示，如：Shall I open the door?10、should的基本用法(1)should作为情态动词可以表示“建议”或“劝告”，有“应该”之意，如：You should learn from each other. (2)should后接完成式表示过去没有做到本来应该做的事情，或是做了本来不应该做的事情。如：You should have give him more help. 11、will的基本用法(1)用于各人称，可以表示“意志”或“决心”，如：I have told him again and again to stop smoking, but he will not listen. (2)在疑问句中用于第二人称，表示说话人向对方提出请求或询问对方的意愿，如：Will you please tell me how to get to the Capital Gymnasium? (3)will可以表示一种习惯性的动作，有“总是”或“会要”之意，如：Every morning he will have a walk along this river.12、would的基本用法(1)would作为will的过去式，可用于各人称，表示过去时间的“意志”或“决心”，如：He promised he would never smoke again.(2)在疑问句中，用于第二人称，表示说话人向对方提出请求或许问对方的意愿时，比用will的气更加婉转，如：Would you like some more coffee? (3)在日常生活中，学用“I would like to”表示“我想要”或“我愿意”之意，以使语气婉转，如：I would like to do Ex.2 first.(4)would可以表示过去的习惯动作，比used to正式，并没有“现已无此习惯”的含义。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表示过去的习惯动作或状态，现在已不存在，在间接引语中，其形式可不变，例如：He told us he used to play foot ball when he was young. 在疑问句、否定句、否定疑问句或强调句中，可有两种形式。疑问句：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 也可写作usent)；否定疑问句：Usent you to/ Didnt you use to be interested in the theatre? 强调句：I certainly used to/ did use to smoke, but it was a long time ago.；其反意疑问句或简略回答中，也有两种形式：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意为“最好”，后接不带to的不定式，例如：- We had better go now . - Yes, we had (wed better/ we had better)./ Hadnt we better stop now? (Had we better not stop now?)/ I think Id better be going. (用于进行时态，表“最好立即”)/ You had better have done that (用于完成时态，表未完成动作) 注：had better用于同辈或小辈，对长辈不可用。(3)would rather意为“宁愿”，表选择，后接不带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表选择，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不是情态动词，would 在此是表愿望的实义动词)。虚拟语气的用法一、语气的种类：英语句子中谓语动词的语气有四种：1. 直陈语气（The Indicative Mood）直陈语气用于直截了当地陈述事实、描述状态：He has published quite a number of essays this year .他今年已发表了好几篇论文。2. 祈使语气（The Imperative Mood）祈使语气用于提出请求、命令、建议或是劝告等：Wait outside until you are asked . 请在外面等候，请你进再进去。Lets just take a break, shall we ? 我们休息一会儿，好吗？3. 疑问语气( the interrogative mood ) ：用来提出问题Where are from ?4.虚拟语气（The Subjunctive Mood）虚拟语气用于表示主观愿望和假设的虚拟情况。虚拟语气不太顾及事实的存在，它表现出说话人的主观因素比较多。所以说话人所讲的内容往往是与事实相反的；或是其实现的可能性微乎其微，甚至于没有实现的可能性。当然，有时为了使说话的语气客气、缓和、委婉，也使用虚拟语气。I wish you were more careful .但愿你更细心一些。If I had more money, I would buy a bigger apartment.我要是有再多一点钱，我就买一套更大一些房子。Would you mind shutting the door ? 劳驾您把门关上。二、虚拟语气的种类：虚拟语气用来表示说话人的主观愿望或假想，所说的是一个条件，不一定是事实，或与事实相反。虚拟语气在条件句中应用比较多；条件句可分为两类，一类为真实条件句，一类为非真实条件句。非真实条件句表示的是假设的或实际可能性不大的情况，故采用虚拟语气。三、真实性条件句1.真实条件句用于陈述语气，假设的情况有可能发生,各种结构如下：条件从句 主句一般现在时 shall/will + 动词原形祈使句 情态动词一般现在时If he es, he will bring his violin. 如果他来，会带小提琴来的。【典型例题】The volleyball match will be put off if it_.A.will rain B. rains C. rained D. is rained【解析】B 真实条件句主句为将来时，从句用一般现在时。【点拨】1. 在真实条件句中，主句不能用be going to表示将来，该用shall, will.（错） If you leave now, you are never going to regret it.（对） If you leave now, you will never regret it.2. 表示真理时，主句谓语动词不用shall （will） +动词原形，而直接用一般现在时的动词形式四、非真实条件句1.虚拟语气可以表示过去，现在和将来的情况，时态的基本特点是时态往后推移2.虚拟语气表时间从句主句例句与现在事实相反的假设一般过去时（ be 用were）Would / should / could / might / ought to + 动词原形1.If they were here, they would help you.2.If we had enough money , we would buy a puter .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 .与过去事实相反的假设过去完成时Should / would / could / might + have+ 过去分词1.If he had e 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 .与将来不大可能发生的事情的假想一般过去时 / should/would + 动词原形Should / would / could / might / ought to + 动词原形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 ?与将来事实相反的假设were+ 不定式Should / would / could / might / ought to + 动词原形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、混合条件句(也叫：错综时间条件句)有时，主句与从句的动作发生在不同的时间，主句从句谓语动词的虚拟语气形式因时间不同而不同，这种条件句叫做混合条件句If you had asked him yesterday, you would know what to do now. 如果你昨天问过他，今天就知道做什么了。（从句与过去事实相反，主句与现在事实相反。）1.If it had rained last night（过去）, it would be very cold today （现在）.如果昨晚下过雨，今天就会很冷了。2.If youd listened to me , you wouldnt be in such trouble now . 如果你听了我的话，你现在也不会这样麻烦了3.If it hadnt been for her care , I should not be speaking to you now. 如果不是她照顾我，我也不会在这里和你讲话4.If the doctor had e in time , any would still be alive . 如果医生及时赶到，AMY现在还活着。六、含蓄条件句：含蓄条件句是指非真实条件句中的条件从句有时不表出来,只暗含在上下文中。含蓄条件句常见的表达方式有:1.定语从句和状语从句Anyone who had married such a girl as she would have been regretful . 谁娶了像她这样的姑娘都会后悔的help was promised where it should bee necessary . 要是需要的话就答应给予帮助2.介词及介词短语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 .要不是有养老金，他都要饿死了Without your help , I couldnt have achieved all this . 要不是有你帮助我不会取得这些成就With his aid , you would succeed . 如果有了他的帮助，你就会成功。Plants would die without water on the earth . 地球上如果没有水，植物就会死的But for the fog we would have reached our destination long ago . 要是没有雾的话，我们很早就到目的地了Under more favourable conditions we could have finished the task . 如果条件对我们更有利，我们就会把工作完成得更好3.连词otherwise, or, butHe would have given you more help , but he has been so busy . 他本来要多给你一些帮助，只是他太忙了Seize the chance , otherwise you would regret it . 如果不抓住这个机会，你会后悔的He felt very tired yesterday , or he would have helped you . 他昨天觉得很累，不然会帮你的4.通过分词短语表示条件Given more time, we could have done it better.Legalizing this drug would have disastrous consequence . 使毒品合法化会有灾难性的后果5.用动词不定式表示条件It would be a mistake not to help him.She would have done anything to make amends . 她会做任何事来弥补特殊情况：情态动词在日常用语中用得很多，使句子显得比较委婉；这类谓语算不算虚拟语气很难说，但有两点是肯定的：一是它们不受时态的影响，虽然形式接近过去式，却常指现在的情况，而且和虚拟语气在形式上一致，在不少情况下几乎可以说是一种含蓄的虚拟条件句；二是它们不表示事实，常带有主观色彩，因而使句子显得很委婉。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、虚拟语气在宾语从句中的运用1.虚拟语气用在would rather，would（just）as soon，would sooner，would prefer（希望）等后接的宾语从句中。意指某人宁愿让另一个人做某事，其后的宾语从句的谓语动词需用虚拟语气。若表示现在或将来要做某事，从句谓语动词需用一般过去时，表示过去已经做的事，从句谓语动词用过去完成时。The manager would rather his daughter did not work in the same office经理宁愿她女儿不与他在同一间办公室工作。To be frank，Id rather you were not involved in the case坦率地说，我希望你不要卷入这件事。You dont have to be in such a hurryI would rather you went on business first你没有必要这么着急，我宁愿你先去上班。Id rather you didnt make any ment on the issue for the time being我倒希望你暂时先不要就此事发表意见。Frankly speaking ，Id rather you didnt do anything about it for the time being坦白地说我宁愿你现在对此事什么也不做。Wouldnt you rather your child went to bed early？为什么你不愿让你的孩子早点上床呢？【点拨】若某人愿自己做某事， would rather后用动词原形 I would rather stay at home today would ratherthan中用动词原形 I would rather stay at home than go out today2.在表示命令、建议、要求等一类动词后面的从句中，像order, suggest, propose, require, demand, request, insist, mand,insist + （should） doI suggest that we （should） hold a meeting next week. 我建议下周召开个会议。He insisted that he （should ） be sent there.他要求被派到那儿去。【点拨】如suggest, insist不表示建议 或坚持要某人做某事时，即它们用于其本意暗示、表明、坚持认为时，宾语从句用陈述语气。判断改错： （错） You pale face suggests that you（should）be ill.（对） Your pale face suggests that you are ill.（错） I insisted that you（should）be wrong.（对） I insisted that you were wrong.3.wish的用法1）wish后面的从句，表示与事实相反的情况，或表示将来不太可能实现的愿望时，其宾语从句的动词形式为： 主句 从句从句动作先于主句动词动作（be的过去式为 were） 现在时 过去时从句动作与主句动作同时发生（had + 过去分词） 过去时/现在时过去完成时将来不大可能实现的愿望将来时/现在时 would/could +动词原形I wish I were as tall as you.我希望和你一样高He wished he hadnt said that. 他希望他没讲过那样的话I wish it would rain tomorrow. 我希望明天下雨就好了I wish that he werent so lazy .但愿他不那么懒He wishes that he were a teacher . 他希望他是个老师就好了I wish that he had not made so much fuss about it . 但愿那时他对这事不那么大惊小怪I wish that the rain would stop . 要是雨停就好了2）在“it is wished that”句型以及作名词所引起的表语和同位语从句中也要求使用虚拟语气，用法同上。3) wish to do；wish sb / sth to doI wish to see the manager. = I want to see the manager. 我希望见一见经理。I wish the manager to be informed at once. （= I want the manager to be informed at once.）我希望经理能马上得到消息八、 虚拟语气用在表语从句或同位语从句中当某些表示建议、请求、命令等主观意向的名词作主语时，其后的表语从句或同位语从句需用虚拟语气，其表达形式为should 动词原形或直接用动词原形。这类名词常见的有：advice，suggestion，proposal，order， demand，desire，request，requirement，remendation , aim , wish , necessity , preference , motion , plan，idea，resolution等。We are all for your proposal that the discussion be put off我们都赞成你提出的将讨论延期的建议。The suggestion that the mayor present the prizes was accepted by everyone由市长颁发奖金的建议被每个人接受。Any proposals that john should be dismissed must be resisted . 必须抵制任何开除JOHN的提议His idea that we should take up the matter with a special board is fairly resonable . 他建议我们以一个专门委员会处理这件事，这的确有道理Our suggestion is that we should put on a play at the english evening . 我们建议在英语晚会上演一个剧九、在主语从句中的应用It is / was + necessary + that + 主语 + should + 加动词原形，should 可省略，表示建议、命令、请求、道歉、怀疑、惊奇等可用的词有：suggested, ordered, required, proposed, demanded , requested, insisted , important, necessary, natural, imperative, strange , a pity, a shame, no wonder , essential , advisable , mandatory , obligatory , vital , pulsory , crucial , fitting , better , best , appropriate , remended 十、虚拟语气在其他状语从句中的使用1. 虚拟语气用在目的状语从句中在由lest , for fear that , in order that , so that , in case of 等引导的目的状语从句中需用虚拟语气，表示“以防，以免”等意思，其谓语动词多由should / could / might + 动词原形构成，should也可省略。He was punished lest he should make the same mistake again他被处以惩罚以免他再犯。I reminded her twice of it lest she should forget . 我提醒她两次，怕她忘记I will not make a noise for fear that I should disturb him . 我不会出声的，以免打扰他I have e all the way here in order that you should understand me . 我到这里来为的是你能理解我He put his coat over his son in case he should catch cold . 他把大衣盖在儿子身上以免他着凉注意：如果 in order that 和 so that 前的主句是现在时，其后的从句有时也可用 can , may + 动词原形。Ask him to hurry up with the letters so that I can sign them . 让他带着信赶快来以便我签字在以lest 和in case 引导的目的状语从句中谓语动词若属于过去时，一般要用虚拟语气， should + 动词原形，若谓语动词不是过去时，也可以用成述语气。take warm clothes in case the weather is cold . 带上厚衣服以防天变冷。2.虚拟语气在方式状语从句中在as if（as though）引导的方式状语从句中，常用虚拟语气，表示似乎，好象的意思，其动词形式与wish后接宾语从句中的形式相同。Alan talked about Rome as if he were a Roman艾伦谈起罗马来好像他是个罗马人一样。I feel as if I were ten years younger . 我觉得我仿佛年轻了10岁He talks about pyramids as though he had seen them himself . 他谈起金字塔来，就好象亲眼见过似的I feel as if we had known each other for years . 我感到我们好象已经认识多年了It looks as if it might rain . 看上去好象要下雨十一、虚拟语气的倒装形式在书面语中，如果条件从句含有 were, had, should，可将连词 if 省略，再将 were, had 或 should 移至句首，构成非真实条件句的倒装语序Were they here now, they could help us. =If they were here now, they could help us.他们现在在的话，就会帮助我们了。Had you e earlier, you would have met him. =If you had e earlier, you would have met him.你来得早一点，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，庄稼就有救了。【典型例题】_ 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. 在虚拟条件状语中如果有were, should, had这三个词，通常将if省略，主语提前, 变成 were, should, had +主语的形式。但要注意，在虚拟条件状语从句中，省略连词的倒装形式的句首不能用动词的缩略形式。如我们可说Were I not to do, 而不能说 Werent I to do.e.g. Had you been here just now, you would have met her. 你要是刚才在这儿，就见到她了。Were I not busy, I would have e. 假如我不忙，我就会来了。十二、其他句型1.虚拟语气用在It is 形容词that的主语从句中在某些表示愿望、建议、请求、命令等形容词后的主语从句中，需用虚拟语气。其表达形式为should 动词原形或省略should直接用动词原形。这类形容词有 advisable（合理的），appropriate（适当的），pulsory（必须的），crucial（紧急的），desirable（理想的），essential（必要的），imperative（迫切的），important（重要的），incredible（惊人的），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（紧迫的）， vital（极为重要的）。It is essential that these application forms be sent back as early as possible这些申请表应尽早地寄回，这是很重要的。It is vital that enough money be collected to fund the project重要的是募集足够的钱，为这个项目提供资金。2.虚拟语气用在It is 过去分词that的主语从句中在It is 过去分词that的主语从句中，常用虚拟语气，表示愿望、建议、请求等主观意向，谓语用 should 动词原形或省略should只用动词原形。这类过去分词有：decided，demanded，desired，insisted，ordered，proposed，suggested，remended，requested， required等。It is desired that we（should）get everything ready this evening希望我们今晚一切都准备就绪。3.虚拟语气用在It is（about high）time that定语从句中在It is（abouthigh）time that定语从句中需用虚拟语气，表示“该做的时候了”，其动词形式用一般过去时或should 动词原形.Its already 5 oclock now,Dont you think its about time we went home？已经5点钟了，你不认为我们应该回家了吗？【点拨】在this is the first time second time that句型中，从句中谓语动词用陈述语气完成时态Is this the first time that you have visited Hongkong？这是你第一次参观香港吗？Its time to do something有别于Its time that4.比较if only与only ifonly if表示只有；if only则表示如果就好了。If only引起的句子，一般过去时或would+动词原形表示现在或未来事实相反，过去完成时表示与过去事实相反，也可用于陈述语气.I wake up only if the alarm clock rings. 只有闹钟响了，我才会醒。If only the alarm clock had rung. 当时闹钟响就好了。If only he es early. 但愿他早点回来.If only we knew where to look for him. 我们要是知道到哪里去找他就好了.If only I had listened to my parents. 要是我听取了父母的话该多好啊.5.but 或 but that 表达的含蓄条件的特殊含义but 或 but that 做“如果不”解，意思相当与“if not”，其后面不可接虚拟模式，应接陈述式的现在时动词或过去时动词，即but that + 主语 + 现在时动词 / 过去式动词，而主句要用虚拟式。But that you help him , he would fail . 如果没有你的帮助，他会失败的.But that you helped him , he would have failed . 如果没有你的帮助，他早就失败了.6. need “不必做”和“本不必做”didnt need to do表示过去不必做某事, 事实上也没做；neednt have done表示过去不必做某事, 但事实上做了.John went to the station with the car to meet Mary, so she didnt need to walk back home.约翰开车去车站接玛丽，所以她不必步行回家了.John went to the station with the car to meet Mary, so she neednt have walked back home.约翰开车去车站接玛丽，所以她本不必步行回家了。 （Mary步行回家了，没有遇上John的车.）【典型例题】There was plenty of time. She _.A. mustnt have hurried B. couldnt have hurriedC. must not hurry D. neednt have hurried【解析】 D neednt have done. 意为本不必，即已经做了某事，而时实际上不必要。Mustnt have done 用法不正确，对过去发生的事情进行否定性推断应为couldnt have done, 不可能已经。must not do 不可以（用于一般现在时）.7.不定式的完成时用在 intend , mean , plan , suppose 等动词后，表示原打算做而实际未能做而实际未能做成的事，因而含有虚拟的意思.8. need /