一 1) 2) 3) 概述 情态动词的共性 情态动词一般直接加动词原形, 除 ought + to do sth .在否定句或疑问句中 to 可以省略 情态动词不会因为主语的人称与数的变化而发生变化 当情态动词表达与说话同时或说话之后的情况,直接加动词原形(do sth/be done) .在简略回答时直接用情态动词 (---Can you dr
ive a car? ---- Yes, I can) （1）She said he might come to the farewell party (表达说话之后的情况) （2）She told me that he must be ill, for his face was pale(表达与说话同时情况) 4) 当情态动词表达说话时已发生的情况,加动词完成式( have pp/have been pp) 在简略回答时用情态动词+ have (---- Did he go to the cinema? ---- No, he should have, but he had to finish a report) (1) She may have been there yesterday (2) She should have come to his rescue when he was trapped in the elevator last night (3) He must have been praised at the meeting the other day 二情态动词用法 1 can 1)表示现在或将来的能力, 2)表示可能性“可能” （1）在肯定句中指逻辑推理的可能性，不指具体的事情的可能性，即泛指的可能性但在否定句或疑问句中可以表达具 体一件事情的可能性 A: Driving carelessly can be dangerous B: Too much stress can drive a person mad C: Everybody can make mistakes in his life D: There being too much snow on a highway can lead to accidents (2) 在否定句中表示“不可能”A: He can?t be hungry B: She can?t have been criticized at last week?s meeting C: She can?t possibly be tired (3) 在疑问句中表示“可能吗？”A: Can she have been to the scenic spot last Friday? (4) S + can have (been)+ pp 表示“可能已发生某事” ，一般用在否定句或疑问句，如： Can she have been to the scenic spot last Friday? (5）在肯定句中还可以表示“有时可能” A: Scotland can be very cold in winter B: He is a bad-tempered guy, but he can be quite charming when he wishes C: You can be very annoying 总之 can 表示可能性“可能”时可以用在肯定句、否定句和疑问句中。 3)表示“允许” ，相当于 may, can?t 表示“不可以,不能”(1) You can park here (2)He can?t take the magazine out of the library 4)表示“可以”,在疑问句中主语常是第一人称或第三人称 如： （1） Can I watch TV after I have finished my job? (2) Can he do me a favor by opening the door? 2 could 1) 表示过去的能力 （1）I could climb any tree when I was young (2) I got up early so that I could catch the early bus 2) 表示过去的可能性 （1）He could be very naughty when he was a boy(2) She said that he couldn?t be hungry(3) She told me that he couldn?t have left here 3) 有时 could 可以代替 can 表示现在或将来的情况(1) Could (=Can) you send me an application form?(表示“委婉提出请 求”) (2) Could this be true? （表示“可能” (3) ---- Who is the man? ---- He could/may/might/be our principal（表示“可 ） 能” ）注意：在肯定句中一般不用 can 表示具体的某一件事情的可能性，但可以用 could 在肯定句中表示具体的某一件 事情的可能性） 4）can have pp 与 could have pp 的区别 A: can have pp 一般只能表示可能已发生了某事，用在否定句或疑问句中，一般不用在肯定句中且不表达虚拟语气 B: could have pp 既可以表示可能已发生了某事，等于 can have pp,也可以表达虚拟语气“本来能够做某事但实际未做”注
意：当主句的谓语动词是过去式时，那么从句在表示可能已发生了某事时，只能用 could have pp 如： He said that she couldn?t have committed suicide 3 may 1)表达 “可以” 在疑问句中主语常用“I”(1) May I have your attention, please? (2) May I have your name? (3) You may watch TV after you have finished your homework（4）You may come if you wish (5) Dogs may not be taken into the houses 2) 在肯定句表示“可能” ，常指根据具体的已知的信息，表达具体的某一件事情的可能性。如果表示说话同时或之后 的情况用 may do sth；如果表示说话时已发生的情况用 may have (been) pp；如果表示说话时正在发生的情况用 may be +doing；如果表示过去某一具体的时间正在发生的情况用 may have been doing 在否定句中表示“可能不”, 在表示 “可能”时，一般不用在疑问句中(1)His face is pale; he may be ill (2) --- Who is the man speaking to our father?---- He may be our new headmaster (3) His room is dark; he may have gone out for a drive/walk/swim/rest (4) --- Where is the general manager? --- He may have seen the doctor, for he has caught a bad cold (5) He may have been watching TV at nine last night (6) She may be commenting on the newly released film now 3) may 在 so that/in order that + 目的状语从句中表达 “可以” 如:He works hard in order that he may be admitted to that famous college 4) may 在让步状语从句中表达 “可能”(1) No matter what you may have done, I have no interest(“may have done” 从句谓语动词所表示的时间明显在主句所表示的时间之前)(2) Whoever you may be, he won?t let you in(“may be” 从 句谓语动词所表示的时间与主句所表示的时间同时)（3）动词原型 + what + S + may, + 主句 A: Cost what the book may, I?ll take it(不管这书花多少钱,我都买) B: Come what may, I?ll take the side of you(不管发生什么事, 我都支持你) 5)may 在祝愿语中的用法, May + 主语 + 动词原型!(1) May you succeed! (= Wish you success)(2) May all of you be happy!(= Wish all of you happiness!) 6)may 在常用句型中的用法,(1) S + may well do sth(很可能)如: She may well drop in for some tea on her way to work (2) S + may/might as well do sth (不妨做某事,表示与说话同时或之后的情况)如:We may as well stay at home watching TV tonight (3) S + may /might as well have pp (不妨做某事,表示说话时已发生的情况)如:You may as well have gone on an outing last week, but you just stayed at home doing nothing (4)I wish to do sth, may I? 4 might may 的过去式,一般表示过去的情况 1) “可以”(1) I asked the acting manager if I might go home half an hour earlier today (2) He asked me if he might use the phone 2) “可能,也许”(1) He said that he might be late with the supper(2) I guessed he might come tomorrow(注 意:在以上的句中都不能用 may 代替 might,因为当主句的动词是过去式时,从句中的情态动词也用过去式)(3) He might/may/could be our new English teacher(4) She might/may/could be watching the close football match(5) Tom might/may have finished the demanding task(6) ---- Can he have left his bag in the library? ------ Yes, he might/may have(注意:这里的 have 不能省略) 3) 有 时 might 代 替 may 表 示 现 在 的 情 况 , 语 气 更 婉 转 或 可 能 性 更 小 (1) Might I use your phone? (2) He might/may/could tell his wife the news when he gets to the destination (3) He might/may/could be depending on you to give him a helping hand 4) may have pp 与 might have pp 的区别 (1) may have pp 表示“可能”一般只用在肯定句“可能”或否定句中“可能不” 而不表示虚拟语气(2) might have pp 既可以表示“可能”也可以表示虚拟语气 “过去本来可以做但实际未做” 注意： 主句 的谓语是过去式时,从句中只能用 might have pp 表示“可能” 5 must 1) 表示必然性“一定”
(1) All of us must die 2) 表示“必须,一定要,得”(1) You must cut down on smoking (2) I must remember to go to the bank today (3) I?m afraid I must be going 3) 表示“义务”(1) Parents must send their children to school 4)在肯定句中代替 need 表示“有必要” (1) --- Need I finish the exercises before I watch TV? ----- Yes, you must/No, you needn?t (2) You must get up early tomorrow morning 5) mustn’t 表示“不得,禁止,一定不要” (1) You mustn?t take photos here (2) We mustn?t be late for the meeting 6) 表示“偏偏”(1) When I was busy cooking, the telephone must ring (2)When he was about to go to work, an unexpected visitor must come to see him (3) Why must you buy such an expensive dress when you are short of money? 7）表示推测“一定”,只能用在肯定句中。 A:表示对现在的情况推测 must be + adj./n/adv.(1) He must be hungry now (2) Judging from his accent, he must be from Beijing; B: must be doing 表示对现在或将来正在进行的情况推测（1） He must be delivering a speech this time tomorrow C: must have (been) pp 表示对已发生的情况推测(1) He must have been in Beijing last week (2) She must have been criticized at last night? meeting; D: must have been + doing 表示对过去某一具体的时刻正在发生的情况推测 (1) You must have been playing basketball at four yesterday afternoon 6 must may 与 can 在表示推测时的用法上的区别 1) can 可以用在肯定句“可能”,否定句“不可能”或疑问句“可能吗?” 2)may 可以用在肯定句“可能”, 否定句“可能不”,不用在疑问句 3)must 只能用在肯定句中“一定” 4)在肯定句中 can 与 may 都表示“可能”,但有区别 (1)can 在肯定句中指逻辑推理的可能性，不指具体的事情的可能性，即泛指的可能性 (2) can 在肯定句中还可以表示“有时可能” (3) may 在肯定句表示“可能” ，常指根据具体的已知的信息，表达具体的某一件事情的可能性。 7 will 1) 助动词,帮助构成将来式 (1) will do sth (一般将来式) (2) will be doing sth(将来进行式) (3) will have done sth(将来完成式) 2) 表 示 “ 请 求 ”, 用 在 疑 问 句 中 且 主 语 常 是 you (1) Will you please sit down? (2) Open the door, will you? 3) 表示“愿意” (1) I will give you a lift to the airport (2) If you will go to the cinema with me, I?ll appreciate it 4) 表示“现在习惯性动作与行为” (1) Each time he comes here, he will sit for hours talking about almost everything (2) On Sundays she will call on her teacher 5) 表示“客观规律” (1) Oil will float on water (2) He will be twenty years old next year 6) 表示“决心,坚持,承诺” (1) --- Tell him the news when you meet him ----- I will(承诺) (2) ---- Don?t forget to post the letter --- I won?t(承诺) (3) He will have his way (坚持)(4) I won?t let you down in any way (决 心) 8 would 1) 助动词 would do sth 过去将来式 She said that her father would come to see her
2）would 代替 will 表示现在或将来的情况，语气更婉转客气（1）Would you help me with my English?(2) I would/should like/love to pay a visit to the Beijing-based company（3）I would rather stay at home than go on a picnic tomorrow 3）表示过去习惯性动作与行为 （1） He would chat with me when he stayed with me (2) When he was at college, he would call on me 4)表示过去的意愿，常用在间接引语 （1） He asked me if I would help him with his English 9 should 1） should do sth 表示 “应该”表示与说话同时或之后的情况（1）He told me I should drop in on my former English teacher the next day （2） should help each other at school （3） should give me a ring when she gets to her destination tomorrow We She 2) should have done sth 表示 “过去本来应该做某事但实际未做” 等于 ought to have done sth； should not have done sth “过去本来不应该做某事而做了”等于 ought not to have done sth (1) You should have posted the letter on your way home yesterday (2) She shouldn?t have been criticized in the presence of a large audience at last week?s meeting 3)should 在状语从句中的用法 (1)in case +从句（万一）如：You?d better take an umbrella in case it should rain(虚拟语气)/it rains(陈 述语气) (2) for fear that +从句 （惟恐）(3) lest +从句（以免） 10 shall 1) 助动词 如果主语是 I/we 且句子是陈述句，那么可以用 shall 代替 will 表示将来式 2）当主语是第二或三人称时且句子是陈述句，那么 shall 表示“许诺”“命令” ， “威胁”“强制”等 ， （1）It has been announced that candidates shall remain in their seats until all the papers have been collected. （2）You shall have the book when I finish reading it tomorrow 3) 当主语是第一或三人称时且句子是疑问句， 那么 shall 表示征询对方的意见 “好吗？” （1）What shall I do supposing 等 the train is behind time? (2) Shall he open the window for you? (3) Let?s give a performance together at the coming farewell party, shall we? 11 ought ought + to do sth . 1) ought to do sth 表示“应该” 表示与说话同时或之后的情况 (1)He told me I ought to drop in on my former English teacher the next day (2)We ought to help each other at school (3)She ought to give me a ring when she gets to her destination tomorrow 2) ought to have done sth 表示“过去本来应该做某事但实际未做” 等于 should have done sth 或 ought not to have done sth “过去本来不应该做某事而做了”就等于 should not have done sth (1) You should have posted the letter on your way home yesterday (2) She shouldn?t have been criticized in the presence of a large audience at last week?s meeting 注意：ought 一般不用在虚拟语气中 12 need 既可以作情态动词也可以作行为动词或名词 1）名词 (1) the need for sth :The need for fresh water is increasingly large; This will affect the body?s need for vitamin (2)S + be in need of sth/sb：Our school is in great need(demand) of math teachers (3)There is no need to do sth 2) vt.表示“需要”主动意义 （1） He needs a car of his own (2) I need a pen （3）He needed his bike repaired last week (复合结构) (4) we need you to work for us 3) vt.表示“需要”被动意义+ doing (动名词主动形式表达被动意义) 或 to be done (1)The bike needs/requires/wants to be repaired( repairing)
4） vt 表示“有必要” 主动意义 （1） + didn?t need to do sth (= S + didn?t have to do sth) 过去没有必要做某事实际确实未做 如： didn?t need to go to S He work this morning, so he didn?t get up early （2） S + need to do sth 表示现在或将来有必要做某事 如：You need to come to my help tomorrow 5） 作情态动词时，无过去式，表示“有必要” 。一般不用在肯定句中（在肯定句中常用 must 代替） ，常用在否定句， 疑问句或条件句中 （1）I asked him if he need go there(2) I wonder if I need bring my book (3)--- Need I go there? ---- Yes, you must.(4) A teacher needn?t do every exercise but a student must(5) You needn?t stay up far into the night tomorrow （6）If need be“如果 有必要” 13 dare 既可以作情态动词也可以作行为动词，有过去式 dared。 作情态动词时，一般不用在肯定句中，常用在否定句，疑问句或条件句中 但 I dare say “我想” 除外. 作行为动词时， 与其他的行为动词一样， 后跟 to do sth 在否定句中 to 可以省略 1） don?t dare I (to) go out alone at light2) She dare not ask her teacher questions 3) Dare you jump off the fence?
can 和 could
例句 1．“I don?t think Mike can type.” “Yes, he can.” 2．I can speak fluent English now , but I couldn’t last year. 1． As a human being, anyone can make a mistake. 2． I’m confident that a solution can be found. 3． He can be very forgetful sometimes. 4．I may stay at home this weekend.（实际可能性） 5．Peter might come to join us.(实际可能性) 6．It will be sunny in the daytime ,but it could rain tonight.(实际
在肯定句中，表示客观可能 性，并不涉及具体某事会发 生，常用来说明人或事物的 特征（译为“有时会”。要 ） 表达具体某事实际发生的可 能 性 时 ， 不 用 can ， 需 用 could，may，might。 表示请求和允许。 表示请求， 口语中常用 could 代替 can， 使语气更委婉。 表示对现在的动作或状态进 行主观的猜测，主要用在否 定句和疑问句中。 表示惊异、怀疑、不相信等 态度，主要用在否定句、疑 问句和感叹句中。
1．Can we turn the air conditioner on? 2．Any police officer can insist on seeing a driver?s license. 3．In soccer, you can?t touch the ball with your hands. 4．Could you have her call me back when she gets home, please? 5．I wonder if I could just ask you to sign this. 1．It can?t be easy caring for a man and a child who are not your own. 2．Can the man over there be our head master? 1．Can this be an excuse for not giving them help? 2．This can?t be true. 3．How can you be so crazy.
（1） could 用来表示请求时，语气委婉，主要用于疑问句，不能用于肯定句，答语应用 can（即：could 不能用于现
在时态的简略答语中） 。如： ——Could I use your dictionary? ——Yes, you can.(否定回答可用：No, I?m afraid not.或者是 you can?t) 表示推测时，could 不是过去式，只是语气更委婉；若是推测已发生的事或过去的情况，用 can/could have done can 和 be able to 辨析 can(could)和 be able to 都可以表示能力，意思上没有区别。但 can 只有现在式和过去式，而 be able to 则有更多 的形式。如： I?ve always wanted to able to speak fluent English. Those bags look really heavy, are you sure you?ll be able to carry them on your own? 但是，表示在过去某时的某一场合经过一番努力，终于做成了某事，通常不用 could，而用 was/were able to 来 表示。这时，was/were able to 相当于 managed to do 或 succeed in doing。如： After the accident it was a long time before she was able to walk again. The fire was very big, but most people were able to escape from the building. 惯用形式“cannot ?too?”表示“无论怎么??也不（过分）。如： ” You cannot be too careful.你越小心越好。 惯用形式“cannot but+ 不定式（不带 to） ”表示“不得不，只好” 。如： I cannot but admire her determination.我不得不钦佩你的决心。
二．may 和 might
表示允许、 许可。 否定回答一般用 must not/mustn?t, 表示 “禁止、 阻止” 之意， 但也可以用 had better not (最好别)或 may not（不可以） ，语气较为委婉。 在表示请求、允许时，might 比 may 语气更委婉 些。用 May I 征询对方许可在文体上比较正式， 在口气上比较客气， 在日常用语中， Can I 征询 用 对方意见更为常见。
1． May I come in and wait? 2． ——May I smoke here? ——No, you mustn?t(或 No, you?d better not.) 1． Might I borrow your pen? 2． I wonder if I might speak to your son.
表示可能性的推测， 通常用在肯定句和否定句中， 1． It may rain this afternoon. 含有“或许” “大概” “可能”之意；用 might 代 2． She might come to join us this afternoon. 替 may 时，则语气显得更加不肯定。 3． I suppose he might have missed the train. may 用于祈使句表示祝愿 惯用句式： “may as well 或 might(just)as well+动词原形”意 为“最好，满可以，倒不如” ，相当于“had better 或 there is no reason to do anything else. 1． May you succeed. 2． May you live happily! 3． May she rest in peace.愿她安息。 1． There is nothing to do, so I may as well go to bed. 2． You may as well tell us now, we?ll find out sooner or later. 3． I suppose we might as well go home. 4． And if you have to plough the field anyway, you might as well plant it at the same time.
二．must 和 have to 情态动词 用法
表示“必须，应该”之意，语气比 should，ought to 强烈。其否定形式 mustn?t 表示“不准，不应该，禁
1． You must come to school on time. 2． Everybody must obey the law.
止”等意 在回答带有 must 的问句时，否定回答常用 needn?t 或 don?t have to，表示“不必” ，而不用 mustn?t 表示有把握的推测，意为“一定、准是、相必” ，只 用于肯定句中
3． You mustn?t drive so fast in the street. 4． We mustn?t waste any more time. 1．—Must I come back before ten? —Yes，you must. ----No, you needn?t(No, you don?t have to) 1． It must be my mother. 2． You must be hungry after a walk. 3． There must be a hole in the wall. 1． The film is not interesting. I really must go now. 2． I have to go now, because my mother is in hospital. 1．I had to work hard when I was your age. 2．I will have to learn how to use a computer. 3．In order to take the exam, we?ll have to finish the whole book by the end of this month .
“必须，不得不” ，意义与 must 相近。但 must 表示 的是说话人的主观看法， have to 则往往强调客观 而 需要。 must 只有一种形式，即现在式与过去式都是一种形 式，而 have to 则涉及各种人称、时态等方面的变化 形式。
两者的否定意义不同，mustn?t 表示“禁止，不许” 1． You mustn?t go there. ， don?t have to 表示不必。 2． You don?t have to go there.
-how old are you, madam? -if you must know, I?m twice my son?s age(如果你非得知道，是我儿子年龄的两倍)
四．shall 和 should
用于第一、三人称构成的疑问句，表示征求对方 意见或请求指示,其意为“要不要”、“…好吗”： 1 用于第二、三人称陈述句中，表示说话人给对 方的命令、警告、允诺、威胁、命令、规定、必 然性等 2 表示强制，用于法令、条约、规章中，意为“必 须，应该”。
1． Shall I open the window? 2． Shall we say 6 o?clock, then? 3． Shall he come to see you? 1． Don?t worry, you shall get the answer this afternoon.(允诺) 2． He shall be sorry for it one day, I tell you. （警告） 3． You shall do as I say. (命令) 4． If you children don?t do as I tell you, you shall not go to the party. (威胁) 5． The Persons under 18 shall not be employed in night work．不满十八岁的人不 得雇佣干夜间工作。(表规定) 6． That day shall come(表必然性) 7． Candidates shall remain in their seats until all the papers have been collected. 试卷完全收回后，应试人才能离开座位。
1． What should I do? 2． Should I trust him? 3． You should read his new book.
表示推测，用在肯定句中，对现在的情况或可能 1． It should be a nice day tomorrow. 发生的事的主观推测或期待。意为“想必，大概， 2． It ?s nearly 7 o?clock .Jack should speak in such a way. 或许” 。 【注】should 表示推断时，语气较肯定，通常是 3． He should be around sixty years old. 指非常可能的事(因为暗示有一定的事实依据或 合乎常理)，而 may, might, could 等表示推测 时，则语气较不肯定，尤其是 might, could。 还可以用在 if 引导的条件句中，表示一件事听起 1． Ask Tom to ring me up if you should see him. (你 来可能性很小， 但也不是完全不可能， 相当于 “万 万一见到汤姆，请让他给我打个电话) 一”的意思。从句谓语用 should+动词原形构成， 2． Should I be free tomorrow, I?ll come. (万一我明天 主句都一定用虚拟语气 有时间，我就过来) 3． If things should change suddenly, please let me know. (万一情况突变，请通知我) 1should 表示意外或惊讶 1． It’s strange that he should come so late. 2 用于疑问句或感叹句中， 表示意外、 惊异的情绪， 他竟然来这么迟真是奇怪。 意为“竟会” ，与 why，what，how，who 连用， 2． I’m sorry that this should have 如果是疑问句，则不需要回答。 happened. 我很遗憾竟然发生这种事。 3． I’m surprised that he should say so. 他竟 这样说，这使我很惊讶。 4． Why should anyone want to marry Tony? 5． Don?t ask me. How should I know?
五．will 和 would
用于表示意志或意愿或决心。will 指现在， 1． He is the man who will go his own way. (他首歌自行其 would 指过去。 是的人。) 2． They said they would meet us at 10:30 at the station. 表示请求、建议等和 you 连用，用 would 比 1． Will you please take a message for him? 用 will 委婉、客气。 2． Would you please tell me your telephone number? 表示习惯或倾向，意为“总是，惯于” 。will 1． Fish will die without water. 至现在，would 指过去。 2． People will talk. (人们总会说闲话。) 3． When we worked in the same office, we would often have coffee together. 表示推测，意为“很可能，大概” 。will 表 示推测比 should 把握大，比 must 把握小。 表示功能，意为“能，行” 。惯用形式：will do/would do 表示“解决问题”“就行” 、 。 用于否定句中，意为“不肯”“不乐意” 、 1． These things will happen. 2． That will be the messenger ringing. 3． It would be about ten o?clock when he left home. 1． That will be all right. 2． Either pen will do. 3． It would not do to work too late.（工作太晚不行。 ） 1．I won?t listen to your nonsense. 2．No matter what I said, he wouldn?t listen to me.
特别说明：would 与 used to 辨析
would 可用来表示过去反复出现的动作，但不能表示过去存在的状态，所以我们不能说： “she would be a quiet girl.”
另外，would 强调过去某种特定情况下的活动，是完全过去的事情，同现在没有联系。而 used to 则着眼于过去和现在 的对比，隐含现在已不存在，动作或状态都可表示。Would 可以表示不规则的习惯，used to 则不可。如： He used to be a naughty boy and cause trouble. I used to get up at six in the morning. Sometimes she would take a walk in the neighboring woods. In those days, whenever I had difficulties, I would go to Mr. Chen for help.
六．need 和 dare
情态动词 用法 例句
用于表示“需要，必要”之意。做情态动词时， 1．—Need we leave soon? —Yes, you must.(No, you needn't, or don?t have to) 仅用于否定句和疑问句，只有现在时，过去式 要用 needn't have， 疑问式用 need+人称?,否定式 2．You needn't have hurried. 用 need not(即 needn't） ， (=It was not necessary for you to hurry，but you did).你 当时不必这么匆忙。 做实义动词时，其变化与一般的实义动词相同， 1. 后接带 to 的不定式（need doing = need to be need done ）,过去式用 needed、did you need?和 didn't need,肯定式用 needs/needed/need,疑问 式用 do、does、did 提问，否定式要在前面加 A job like nursing needs patience and understanding.(need+名词， need understanding=need to be understood,需要被理解) 2．He needs to see a doctor.(need to do) 3．Do you still need volunteers to help clean up after the party?(need somebody to do something) 4．They didn't need to start so early.(do not need to do) 1．—Dare you tell her the truth? —Yes, I dare. /No, I daren?t. 3． How dare you accuse me of lying! 4． He daren?t admit this. 1． Only a few journalists dared to cover the story. 2． He doesn?t dare (to) go there alone. 3． Don?t you dare (to) touch it?
用于表示“敢于”之意。做情态动词，没有人 称和数的变化，主要用于否定句、疑问句和条 件状语从句中 用作实义动词时，其变化与一般的实义动词相 同。在肯定句中，dare 后接带 to 的不定式；否 定句中，dare 后既可接带 to 的不定式，也可接 不带 to 的不定式。
表示“应该”之意 ought to do 表示推测。注意与 must 表示推测是的区别
1． You ought to take care of him. 2． —Ought I go now? —Yes, you ought to. /No, you oughtn?t to. 1． He must be home by now. (断定他已到家) 2． He ought to be home by now. (不十分肯定) 3． This is where the oil must be. (比较直率) 4． This is where the oil ought to be. (比较含蓄)
说明：should 与 ought to 表示“应该”时的区别
should 表示自己的主观看法，而 ought to 的语气中，含有“按道理应该??”之意。若要反映客观情况或涉及法 律义务和规定，一般用 ought to。如：
You should help them with their work. You are his father. You ought to get him to receive good education.
八． “情态动词+have done”用法
must have done
表示主观上对过去已经发生的行为进行 1．She must have gone through a lot. 推测，意为“想必，准是，一定做了某事” 2．He must have visited the White
may/might have done
表示对过去已发生行为的推测，意为“也 许/或许已经（没有）??“。一般用于肯 定句或否定句中， 不用于疑问句。 might 用 则表示语气更加不肯定。
can?have done cannot have done
表示对过去发生的行为的怀疑和不肯定， 通常用在否定句和疑问句中。 （can 换成 could 时语气委婉）
could have done
可用于肯定句中，表示“可能已经??” 之意，此外，还可以表示过去能做而没做 的事，有一种对过去为付诸实施的事情的 惋惜。
might have done
表示“本来可能??，但实际上没有发生 的事情” 。另外，还可以表示“本来应该 或可以做某事”之意，含有轻微的责备语 气。 用于肯定句时，表示本该做某事，而实际 上未做；用于否定句时，则表示不该做的 事反而做了。
should/ought to have done
needn?t have done
表示做了本来不必去做的事。 注意： didn?t need to do 表示“没必要做而实际上也没 有做某事”
House during his stay in the United States. 1．You may have learnt the news. 2．He may not have heard his name called. 3．Sorry I?m late. I might have turned off the alarm clock and gone back to sleep again. 1．Where can she have gone? 2．Could he have done such a foolish thing? 3．The boy can?t have finished reading the book so soon because it is difficult even to an adult. 1．He could have killed himself driving at a dangerous speed. 2．You could have been more considerate. 3．You could have done better, but you were too careless. 1．You should not swim in that sea. You might have been eaten by a shark. 2．He might have given him more help, thought he was busy. 1．He should have known that the police would never allow this sort of thing. 2．You shouldn?t have done it so carelessly. 3．You ought to have returned the book earlier. 4．You ought not to have refused his offer. 1．You needn?t have watered the plants, for it is going to rain. 2．I didn?t need to buy the dictionary. I had a copy at home.
had better have done
用于事后的建议，含轻微责备的口吻，意 为“当时最好做了某事” ，其否定式 had better not have done 表示相反的含义。 表示“当时宁愿做了某事” ，其否定式 would rather not have done 表示相反的含 义，两者都表示“后悔”之意。
1．You had better have started earlier. 2．You had better not have scolded her. 1．I would rather have taken his advice. 2．I would rather not have told him the truth.
would rather have done
1. 大多数情态动词（除表‘能力、许可、意志’外） ，都可以表示推测，其程度有差异。 按可能性程度的高低排列为： must ﹥ will ﹥ would ﹥ ought to ﹥ should 完全肯定 完全可能 很 可 能 ﹥ can ﹥ could ﹥ may ﹥ might 可能 有可能 2. 区分情态动词的否定含义：may not 或许不、可能不 might not 可能不 can’t 不可能 mustn’t 不许、禁止 shouldn’ t 不应该 needn’t 不必
1. 情态动词表推测的反意疑问句，简单来说，就是以情态动词后的时态为淮，如句子里有明确的时间状语，则以其为 准。 2. 以 must 为例： E.g. 1. You must be hungry now, aren’t you? 2. He must be watching TV , isn’t he ? 3 Tom must have lived her for a long time, hasn’t he ? 4. She must have arrived yesterday, didn’t she? 注： 如选择题中 （以 She must have arrived yesterday, didn’ she？为例） t 既有 didn’ she 又有 hasn’ she 则以 didn’ she？ t t t 为最佳答案。 IV 情态动词专项练习与解析 ( ) 1. You _____ return the book now. You can keep it till next week if you like. A. can’t B. mustn’t C. needn’t D. may not ( ) 2. Where is my pen? I _____ it. A. might lose B. would have lost C. should have lost D. must have lost ( ) 3. I wish I _____ you yesterday. A. seen B. did see C. had seen D. were to see ( ) 4. I didn’t hear the phone. I _____ asleep. ( ) A. must be B. must have been C. should be D. should have been 5.If my lawyer _____ here last Saturday, he _____ me from going. ( ) A. had been; would have prevented B. had been; would prevent C. were; would prevent D. were; woul d have prevented 6. He _____ you more help, even though he was very busy. A. might have given B. might have C. may have given D. may give ( ) 7. If it _____ for the snow, we _____ the mountain yesterday. A. were not; could have climbed B. were not; could climb C. had not been; could have climbed D. had not been; could climb ( ) 8. Without electricity human life _____ quite difficult today. A. is B. will be C. would have been D. would be ( ) 9. A computer _____ think for itself, it must be told what to do.
A. can’t B. couldn’t C. may not D. might not ( ) 10. Jenny _____ have kept her word. I wonder why she changed her mind. A. must B. should C. need D. would ( ) 11. We _____ last night, but we went to the concert instead. A. must have studied B. might study C. should have studied D. would study ( ) 12. — Could I borrow your dictionary? — Yes, of course you _____. A. might B. will C. can D. should ( ) 13. Tom ought not to _____ me your secret, but he meant no harm. A. have told B. tell C. be telling D. having told ( ) 14. — If he _____, he _____ that food. — Luckily he was sent to the hospital immediately. A. was warned; would not take B. had been warned; would not have taken C. would be warned; had not take n D. would have been warned; had not taken ( ) 15. Peter _____ come with us tonight, but he isn’t very sure yet. A. must B. may C. can D. will ( ) 16. I told Sally how to get here, but perhaps I _____ for her. ( ) A. had to write it out B. must have written it out C. should have written it out D. ought to wri te it out 18. — Shall I tell John about it? — No, you _____. I’ve told him already. A. needn’t B. wouldn’t C. mustn’t D. shouldn’t ( ) 19. When a pencil is partly in a glass of water, it looks as if it _____. A. breaks B. has broken C. were broken D. had been broken 20. It’s nearly seven o’clock. Jack _____ be here at any moment. A. must B. need C. should D. can 21. — There were already five people in the car but they managed to take me as well. — It _____ a comfortable jou rney. A. can’t be B. shouldn’t be C. mustn’t have been D. couldn’t have been ( ) 22. Johnny, you _____ play with the knife, you _____ hurt yourself. A. won’t; can’t B. mustn’t; may C. shouldn’t; must D. can’t; shouldn’t ( ) 23. The fire spread through the hotel very quickly but everyone _____ get out. A. had to B. would C. could D. was able to ( 24. — When can I come for the photos? I need them tomorrow afternoon. — They _____ be ready by 12:0 0. A. can B. should C. might D. need ( ) 25. — I stayed at a hotel while in New York. — Oh, did you? You _____ with Barbara. A. could have stayed B. could stay C. would stay D. must have stayed ( ) 26. — Will you stay for lunch? — Sorry, _____. My brother is coming to see me. A. I mustn’t B. I can’t C. I needn’t D. I won’t ( ) 27. — Are you coming to Jeff’s party? — I’m not sure. I _____ go to the concert instead A. must B. would C. should D. might ( )
28. — Write to me when you get home. — _____. A. I must B. I should C. I will D. I can ( ) 29. I was really anxious about you, you _____ home without a word. A. mustn’t leave B. shouldn’t have left C. couldn’t have left D. needn’t leave ( ) 30. — Is John coming by train? — He should, but he _____ not. He likes driving his car. A. must B. can C. need D. may 【练习解析】 1．C 从原题中 You can keep it till next week if you like 这一信息句可知，“你不必现在还”。 2．D 从原题中 Where is my pen?这一信息句可告诉考生，“笔丢了”，丢的动作是过去发生的。因此用 must + have done 表示对过 去事实的肯定猜测。 3．C 原题中的 yesterday 这一信息词告诉考生，在 wish 后的宾语从句中，用过去完成时，表示与过去事实相反的愿 望。 4． 从原题中的 I didn’ hear the phone.这一信息可以判断出， must have done 表示过去事实的准确的肯定猜测。 B t 用 5 ． A 从 原 题 中 last Saturday 这 一 信 息 词 可 知 ， 条 件 句 中 用 表 示 与 过 去 事 实 相 反 的 过 去 完 成 时 ， 主 句 用 would + have done。 6．A might have + 过去分词，在次是虚拟语气，表示“本来可以给你更多的帮助”，而事实则是帮助较少。 7 ． C 从 原 题 中 的 yesterday 这 一 信 息 词 暗 示 考 生 ， 该 句 应 选 用 与 过 去 事 实 相 反 的 过 去 完 成 时 ， If it had not been for ? “ 要 不 是 因 为 ? ? ” 。 8 ． D 原 题 中 的 Without electricity 相 当 于 一 个 条 件 句 ： If there were no electricity,故主句用 human life would be quite difficult today. 9 ． A can 可 以 表 示 一 种 客 观 上 的 能 力 ， 本 句 can ’ t ， 表 示 “ 不 能 ， 不 会 ” 。 10 ． B 从 原 题 总 的 “I wonder why she changed her mind”“我不知道为何他改变了主意了。”这句话告诉考生 Janny 没有守诺言。因 此，用 should + have done，表示“过去本应该做某事，而实际上没有做”。 11．C 可参看 10 题。意思是：“昨晚 本应该学习，但是却去听音乐会了。” 12．C 原题中的 could 不是过去时，而表示一种委婉、客气的礼貌用语。因此用 could 提问时，用 can 回答。同样用 would，might 提问，用 will 和 may 回答。[注意]①— Would you rather do such a thing? — Yes, I would. ②— Would you like some tea? — Yes, I would. 这两个对话中的 would rather， would like 是惯用法， 故不能用 will 来回答。 因为在这两个句型中， 不能去替换 would。 will 13 ． A 可 参 看 10 、 15 题 。 该 句 意 思 是 ： “ 汤 姆 本 来 不 该 告 诉 我 你 的 秘 密 ， 但 他 没 有 伤 害 你 的 意 思 。 ” ought not to have done = shouldn’t have done 14．B 从答语中的 Luckily he was sent to the hospital immediately 这一信息句可提示考生，条件句应填表示与过去事实相反的时态。 15．B 从原题中的 but he isn’t very sure yet 这一 信息句可暗示考生，Peter 当晚来的可能性不大。A 是“准来，肯定来”，D 是“将要来”。 16．C 可参看 10、11、 13 题。“本应该”而事实上没有?? 17．D 从原题中 I didn’t see your sister at the meeting 和后文 she would have met my brother 这两个信息句可知， if 条件句中应填与过去事实相反的过去完成时。 可参看 6、 14 题。 18． 你不必告诉他。 7、 A 因为 I’ told him already ve 这一信息句已暗示考生了。 19．C 当 as if 引导虚拟语气的句子是，如果主句与从句中的谓语词所表达的动作同时发生时，as if 后接一般过去时。 例如：He walked as if he were lame.如果从句中的谓语动作发生个在主句谓语动作之前，则用过去完成时。例如： He talked as if he had known the secret.不论主句中的谓语是现在时还是过去时。 20．C 只要考生抓住 nearly 一词和后文 at any moment（随时的意思）这两个信息词语，就能很快选出 C 项，表示逻 辑推测，意思是“快七点钟了，杰克一会儿就该到了。” 21．D 根据句意，是对过去情况的推测。“当时决不可能是 一次舒服的乘车。”must 表示对过去的推测只能用于肯定句。 22．B mustn’t 表示“禁止”；may 表示“有可能”。句子的意思是： “你不可以玩刀，可能会伤你自己。” 23．D 该 题在考考生 could 与 was able to 之间的区别。Was able to 表示在困难的情况下，经过一番周折而“能??”，并且成 功地做了。
24． 该题考查情态动词 should 表推测的用法。 B Can 和 might 都可以表示可能性， might 则语气更加不肯定。 用 Need 表示“需要”、“必需”。Should 可以表示推测，结合实际，合乎逻辑，意为“应当”、“该”。根据第一个说话者 说的 I need them tomorrow afternoon 的语境，可以确定正确答案为 B。 25．A 该题在考查“情态动词+不定式的完成式”的用法，从会话的语境看，空白处应填“could + have +过去分词” 表示过去本来能做到的事而事实上没有做到。 26．B 该题考查表示请求的英语口语，用 will 来向第二人称提问的疑问结构，是表达一种意愿和请求，是以疑问的形 式来表达较为婉转的祈使语气，意思是“请你??，好吗？”，对于这种问句的肯定答语可用 Sure! Certainly! Yes, of course. I’d be glad to 等；否定回答通常是 I’m sorry, I can’t. No, I’m afraid I can’t. I’ m sorry, but ? I ‘d like to, but ?等。 27．D might 表示“可能性”。 28．C 意思是“我会的”。对祈使句的肯定回 答。 29．B shouldn’t have done 为本来不该做某事，而事实上做了。 30．D 用 may not 可表示“可能不”。而 can not 则表示断然的否定推测“不可能