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1、Grammar: Modal verbs,Lectured by RenQiuyu,一、情态动词的特点,1 有词义2 没有人称和数的变化。也就是说，它在任何主语后形式都是一样的，这是情态动词和助动词最大的差异。3 有时态的变化4 不能独立作谓语，后面必须跟动词原形 在情态动词后一般要跟不带to的不定式（ought to除外）,二、情态动词的种类,1) can表示体力、智力上的能力。否定式为cannot, 缩略为cant; 过去式为could couldnteg:We can do things they cant do. Mary can type well and her mother co
2、uld type well when she was young.2) 表示客观可能性eg: Man cannot live without air.3) 表示征求意见或请求许可，表示语气委婉eg:Can I go for a swim this afternoon, Mum? Could you lend me your bicycle? No, sorry, I cant. ( couldnt is wrong) Yes, of course you can.,1. can和 could,4) can 和could 表推测（can用于否定及疑问, could肯定、否定、疑问皆可）can (
3、could) not + V原（link.或状态动词）对现在状态的推测can (could) not + be + doing对现在动作的推测can (could) not + have done 对过去动作的推测eg: a. The young girl cant be our new chairman. Can/ Could the news be true? b. He cant be reading in the reading room, for I saw him in the street just no They may be arguing. But I am interes
4、ted in what they can/ could be arguing. c. The road isnt wet. It cant/ couldnt have rained last night. I dont know why she didnt call me yesterday. Can/ Could she have forgotten my telephone number?5) could have done本能做却没有做, can have done这种结构不存在eg:You could have caught the first train, but you got u
5、p too late.,6) Can/ could与 be able to 的区别A. be able to do sth.也表示能力，可以用于不同时态，前后还可以用情态动词must, may, might以及seem to, used to, appear to等，而can/could只用于一般现在时和一般过去.eg:He is able to (= can) play the piano very well.After three years of hard work, he was able to pass the entrance examination. The large hall
6、 will be able to hold 5000 audience. He seems to be able to work out the puzzling question.B.当用于过去时态时，could表示能力，但有没有做，不知；而was/were able to 指过去某种具体的能力，通过努力并做成功了，相当于managed to或succeeded ineg:He could sing many English songs.Its known that he was able to recite many foreign poems at six.,1) may表示请求许可。疑
7、问式May I.?多为请求允许，通常用于正式文体egMay I come in?No, you cant / may not.Yes, please.No, you mustnt. (强烈禁止，不允许)Yes, certainly Please dont.Sure.Might也可以表示允许，Might I ?和May I.?用法相近. 但might表示请求语气迟疑委婉，回答时应用may表示肯定eg: -Might I ask for a photo of your family? -Yes, you may.2)may用在句子开头，表示祝愿 May + 主语 + 动词原形 + 其它成分eg:M
8、ay you succeed in the coming examination! May all your dreams come true some day!,2. may 和might,3) may和 might表推测（不用于疑问）may/might + V (系动词或状态性动词)对现在状态的推测may/might + be doing 对现在动作的推测may/might + have done 对过去动作的推测eg: a. He may know Alices address. He may not know Alices address. （可能不） He cant know Ali
9、ces address. （不可能） Can it be true? It may be, or may not be. b. Wheres Tom? He may/might be playing football. c. -He seems know the city quite well. - He may/ might have been there before.,1)表示必要性、义务，“应该”、“必须”的意思，否定式mustnt 表示不允许eg You must wait for your turn. You mustnt jump the queue. Must I be hom
10、e before eight oclock? -Yes, you must. ( No, you neednt. / No, you dont have to.)2） have to和must意义相近，意为“不得不”，含有“客观需要使得必须这样做”的意思，有时态、人称的变化, have got to用于口语，dont have to 为否定式，意为“不必要”eg She didnt have to say sorry. Do we have to answer all the questions? Next year I will have to leave this school.3） mu
11、st 表推测（一般用于肯定句）意为：一定 否定式： cant must + V must + be doing must + have doneeg: 情态动词must猜测性的反义疑问句 He must be a doctor, isnt he? （表现在状态， 用be） He must live near here, doesnt he? （表现在动作，用do, does） He must have come here yesterday, didnt he? （表短暂性过去动作，用did） They must have been to Beijing, havent they? （表现在状
12、态，用have, has）,3 must 和 have to,4 will / would; shall,1)will表示意志意愿，用于各种人称，可译为“肯”、“会”、“愿意”等，过去式为would egIf you will allow me, I will see you home. I will have nothing to do with this matter. No matter what happened, he wouldnt say a word. If he kept on making mistakes, I wouldnt make friends with him.
13、2)will用于第二人称，表示有礼貌的请求，would为过去式，但语气更委婉eg Will you kindly hand me the watch? Bring the fruit to the dining-room, will you? - Would you do me a favor? - Yes, I will./ Sure / Of course/ Certainly. No, I wont./ Im sorry I cant. Will/ Would you please do Would you like to do sth. would rather do sth. (th
14、an do sth.),3) would do (used to do)表示过去常常做某事,would后只能接动作性动词而used to 既可以接动作性动词，也可以接状态性动词。 He would go to enjoy some wonderful films at night. He used to be a teacher.4) would have done 用于虚拟，与过去事实相反 If you had helped us, we would have finished our homework ahead of time.5）shall用于第一、第三人称疑问句中，表示说话人征求对方
15、意见或向对方请示。 egShall we go and get some food? When shall he be able to leave the hospital?Shall 用于第二、第三人称，表示说话人给对方的命令、警告、允诺或威胁。 eg. You shall do it./ He shall stay at home. （命令） You shall fail if you dont work hard. （警告） He shall have the book when I finish reading.（允诺） He shall be punished. （威胁）,5 sho
16、uld / ought to,两者意义基本相同，用法也相同1）表示劝告或建议，should语气比ought to 弱，意为“应该”，否定式shouldnt, ought not to意为“不应该”eg You should get everything ready before the examination. He shouldnt be so careless. We ought to be out in the fresh air. We ought not to take risks（冒险）.2）表示应该怎么样却没有怎么样 A. 对现在进行动作 should(ought to ) be
17、 doing / shouldnt (ought not to) be doing eg:You should be washing your clothes. Why are you playing football? You are ill. You shouldnt be working here B. 对过去动作 Should (ought to ) have done (本应该做却没有做) Shouldnt (ought not to) have done (本不应该做却做了) eg:You should have gone over your lessons. I shouldnt
18、 have eaten so much ice cream.3) should 表推测，暗含很大的可能或有根据有把握 The film should be very good. The photo should be ready tomorrow.,6 need,可以既作情态动词又作实义动词1) need用作实义动词，用在肯定句、否定句和疑问句中，有人称变化和过去时形式，后接名词、代词、动名词和动词不定式eg She needs more rest. You didnt need to tell him the news. The TV needs mending / to be mended
19、.2)need作情态动词时一般只用在否定句或疑问句中，没有人称和时态的变化 eg- Need we tell him about it? - No, you neednt / dont have to. You neednt finish writing the report in such a short time. He said he need not go yesterday.3) neednt have done 本不必做却做了 need have done几乎不存在这种结构 Time is enough. You neednt have come in such a hurry.,
20、7 dare,可以既作情态动词又作实义动词1) dare用作实义动词，用在肯定句、否定句和疑问句中，有人称变化和过去时形式，dare(s/d) to do sth, 但在否定句中，后面的不定式可带to, 也可不带toegHe was so brave that he dared to go alone at night at the age of five. He does not dare (to) answer his fathers question. Do you dare to touch it?2) dare作情态动词主要用于否定句、疑问句或条件句中，没有人称的变化，但是有过去式d
21、ared，但I dare say（常用作插入语）除外eg His speech is quite excellent, I dare say, which will win him the first prize. How dare you say I am a liar? No one dared speak about it. I darent ask you, because I thought I must be wrong. If you dare do that again, the teacher will scold you.,情态动词的猜测性用法总结,我们用must（一定）,
22、 can（可能）, could（可能）, may（也许）, might（或许）表示“猜测可能性”。Could , might比can, could在口气上要委婉些。可能性由大到小排列为：must can(could) may might,1）对现在或将来的猜测 Modal. Verb + (not) do sth She must / may / might know Lilys address. He must / may / might leave for Beijing tomorrow. He cant / couldnt / may not / might not be able t
23、o pay the house. - Its not mine. Whose can / could it be? （疑问句中一般不用may, might） - It could be Johns. / It cant / couldnt be Jims.2）对现在进行的动作的猜测 Modal. Verb + (not) be doing sth They must / may / might be waiting at the school gate. He cant be reading in the classroom for I saw him in the street just n
24、ow. She cant / may not / might not be eating anything now.3）对过去动作或已经完成的猜测 Modal. Verb + (not) have done sth He must / may / might have made much progress recently. He cant / couldnt / may not / might not have finished his homework. Can / Could he have got what he wanted?,注：1 must作为猜测只能用于肯定句，mustnt表示
25、不能，不许，不是猜测2 can作为猜测只能用于否定句，疑问句，但could可用于肯定句、否定句和疑问句3 can have done, mustnt have done作为猜测不存在，could have done表示本能做却没有做4 may, might作为猜测一般不用于疑问句,1、English is a language that many people around the world not speak perfectly but at least_ understand.A. may; can B. would; might C. will; must D. could; migh
26、t,【答案解析】根据句意和句子的语气可知，第一空表示一种可能性，用may not speak 可能不会说；第二空表示有某种能力。答案A。,2、Didnt they come to the party last week? Yes. They didnt want to come with us at first, but then we _ persuade them.A. Would B. could C. were able to D. had to,【答案解析】根据上下文语境及讲话人语气，选项动作表示经过努力才完成的。在这种语气的肯定句和疑问句中，常用be able to，在否定句中可用
27、can。答案 C。,3、 I promise her daughter _ get a nice present on her birthday. Will it be a big surprise to her?A. should B. must C. would D. shall,【答案解析】根据讲话人语气可以知道，选项部分表示讲话是给对方的一种承诺，故应该选情态动词shall用于第二或第三人称用作主语的句子结构中。答案D。,4、All of us had a good time in the picnic last Sunday. Pity you werent there. I rea
28、lly _come but I was looking after my mother in hospital.A. mustB. ought toC. need haveD. should have,【答案解析】根据上下文和讲话人语气，选项情态动词表示过去本该做而实际未做的事， 故应选用should have done 或ought to have done。 must do， ought to do表示还未发生的动作。need have done常用于否定或疑问句，表示本来不必干某事。答案 D。,5、Did you scold him for his carelessness? Yes,
29、but _ it.A. I would rather not doB. Id rather not have doneC. I shouldnt doD. Id better not do,【答案解析】根据上下文语境可以知道，选项动作是对过去事情的推测，表示过去已经责怪，而宁愿该事情没有发生之意。故选Id rather not have done，其它三个选项表示对将要做的事情的态度。答案B。,6、Just as we were sitting down to have dinner, the telephone _ ring.A. must B. could C. might D. need,【答案解析】must 在此表示说话人的愿望或感到不耐烦，意思为“偏要”。句意：正当我们吃饭时电话铃偏偏响了。其它选项无此意义，答案A。,
