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1、TEM-4 历年语法考点,第二章 情态动词,情态动词也称为情态助动词。情态动词无人称和数的变化；不能单独使用，必须与其后的动词原形构成谓语。常用的主要情态动词有：can/could/may/might/will/would/shall/should/dare/must/ought to/need/used to等。,一、常用的情态动词 1. can与 could 1) 表示能力（体力、知识、技能），可能，能够。 can此时可用be able to代替。can只有一般现在时和一般过去式；而be able to则有更多的时态。 e.g. Can you lift this heavy box? I
2、ll not be able to come this afternoon.,当表示“经过努力才得以做成某事”时应用be able to，不能用can。 e.g. He was able to go to the party yesterday evening in spite of the heavy rain.,2) 表示请求和允许。此时可与may互换。在疑问句中还可用could, might代替，不是过去式，只是语气更委婉，不能用于肯定句和答语中。 e.g. -Can I go now? - Yes, you can. / No, you cant. - Could I come to
3、see you tomorrow? - Yes, you can. (No, Im afraid not.),3) 表示客观可能性（客观原因形成的能力）。e.g. Theyve changed the timetable, so we can go by bus instead. This hall can hold 500 people at least.,4) 表示推测（惊讶、怀疑、不相信的态度），用于疑问句、否定句和感叹句中 e.g. Can this be true? This cant be done by him. How can this be true?,2. may与 mig
4、ht 1）表示请求和允许。might比 may语气更委婉，而不是过去式。否定回答时可用cant或mustnt，表示“不可以，禁止”。 e.g. -Might/ May I smoke in this room? - No, you mustnt. - May/Might I take this book out of the room? - Yes, you can. (No, you cant / mustnt. ) 【注】 用May I.？征询对方许可时比较正式和客气，而用Can I.？在口语中更常见。,2）用于祈使句，表示祝愿。 e.g. May you succeed! May our
5、 friendship live long. Happy may your birthday be！,3) 表示推测、可能性（不用于疑问句）。might不是过去式，它所表示的可能性比may小。 e.g. He may /might be very busy now. Your mother may /might not know the truth.,4) 用在表示让步的状语从句或分句中，可译为“尽管”。 e.g. Whoever he may be, he should obey the rules. Come what may, Im prepared for it. He would w
6、ork diligently, however rich he might be.,3. must与 have to 1) must 表示必须、必要。在回答引出的问句时，如果是否定的，不能用mustnt（禁止，不准），而用neednt; dont have to（不必）。 e.g. You must come to school on time every day. - Must we hand in our exercise books today? - Yes, you must. - No, you dont have to / you neednt.,2） must是说话人的主观看法，
7、 而have to则强调客观需要，意思是“不得不”。 must只有一般现在时， have to 有更多的时态形式。 e.g. The play isnt interesting，I really must go now. She is always having to make decisions. He has had to reconsider his position.,3) must表示推测、可能性（只用于肯定的陈述句），而have to则不能。 e.g. Youre Toms good friend, so you must know what he likes best. Your
8、 mother must be waiting for you now. 【注】表示否定的推测用cant。 e.g. The person called cant be professor Wang because I just talked to him in the office.,4. dare与 need dare作情态动词用时, 常用于疑问句、否定句和条件从句中, 过去式形式为dared。 e.g. How dare you say Im unfair? He darent speak English before such a crowd, dare he? If we dared
9、 not go there that day，we couldnt get the beautiful flowers.,【注】I dare say或 I daresay为惯用语，意为“我想，我以为”。 e.g. She will keep her word, I dare say. I dare say she will come.,2）need 作情态动词用时, 常用于疑问句、否定句。在肯定句中一般用must, have to, ought to, should代替。 e.g. You neednt come so early. - Need I finish the work today
10、? - Yes, you must. / No, you neednt.,3）dare和 need作实义动词用时， 有人称、时态和数的变化。在肯定句中，dare后面常接带to的不定式。在疑问句和否定句中，dare后面可接带to或不带to的不定式。而need后面只能接带to的不定式。 e.g. I dare to swim across this river. He doesnt dare (to) speak of it. He needs to finish his homework today.,【注】在表示怀疑或否定概念的句子里，若是正式文体，多用情态动词need的肯定式；若是非正式问题
11、，多用实意动词need的肯定式。试比较： I wonder if we need take sleeping-bags. （正式文体） I wonder if we need to take sleeping-bags. （非正式文体） I dont think he need go just yet. （正式文体） I dont think he needs to go just yet. （非正式文体）,5. shall 1）shall 用于第一人称，征求对方的意见。e.g. What shall we do this evening? 2) shall用于第一、第三人称疑问句中，表示说话
12、人征求对方的意见或向对方请示。 e.g. Shall we begin our lesson? When shall he be able to leave the hospital?,3) shall 用于第二、三人称，表示说话人给对方的命令、警告、允诺或威胁。但 shall 所表示的意志是说话人的意志，而非句子中主语的意志。在法律、条约、协定等文件中，shall 表示义务、规定等。 e.g. You shall fail if you dont work hard. (警告) He shall have the book when I finish it. (允诺) If you dont
13、 behave yourself, you shall be punished. (威胁) POWs shall not be ill treated. （法律用语）,6. will与 would 1) 表示请求、建议等，would更委婉。 e.g. Will / Would you pass me the ball, please? Would you please tell me your telephone number?,2) 表示意志、愿望和决心。 e.g. I will never do that again. They asked him if he would go abroa
14、d.,3)would表示过去反复发生的动作或某种倾向。would表示过去习惯时比used to 正式，且没有“现已无此习惯”的含义。 e.g. During the vacation, he would visit me every other day. The wound would not heal.,4) 表示估计和猜想。 e.g. It will be Mr Wang knocking at the door. It would be about ten oclock when she left home.,7. should与 ought to 1）should, ought to表
15、示“应该”，ought to表示义务或责任，比should语气重。 e.g. I should help him because he is in trouble now. You ought to take care of the baby.,2）表示劝告、建议和命令。should, ought to可通用，但在疑问句中常用should。 e.g. You should / ought to go to class right away. Should I open the window?,3）表示推测。should , ought to (客观推测), must(主观推测)。 e.g. H
16、e must be home by now. (断定他已到家) He ought to/should be home by now. (不太肯定) This is where the oil must be. (直爽) This is where the oil ought to/should be. (含蓄),二、情态动词+不定式完成式（have done） 1can / could + have done can / could + have done在肯定句中表示“本来可以做而实际上未能做某事”，是虚拟语气；在疑问句或否定句中表示对过去行为的怀疑或不肯定, 表示推测。 e.g. You could have done better, but you didnt try your best. （虚拟语气） He cant have been to that town.（推测） Can he have got t
