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1、Grammar: Modal verbsLectured 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、情态动词的种类原形过过去式词义词义同义词组义词组 cancould能够够be able to maymight可以、也许许 mustmust必须须have to have tohad to必须须、不得不must had betterhad better最好可以是
2、实义动词实义动词 和情态态 动词动词needneeded需要 daredared敢于 shallshould应该应该ought to willwould愿意 used to过过去常常 ought toought to应该应该should 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 couldnt eg: We can do things they cant do.Mary can type well and her mother could type well when she was young. 2) 表示客观可能性 eg: Man c
3、annot 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 (could) not + V原（link.或状态动词）对现在状态的推测 can (could) no
4、t + 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 noThey may be arguing. But I am interested in what they can/ could be arguing.c. The road
5、 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 up too late. 6) Can/ could与 be able to 的区别 A. be
6、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 will be able to hold 5000 audience.He seem
7、s 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 in eg: 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。疑问式May I?多为请求允许 ，通常用于正式文体 egMay I come
8、in? No, you cant / may not.Yes, please. No, you mustnt. (强烈禁止，不允许)Yes, certainlyPlease 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: May you succeed in the coming ex
9、amination!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 Alices address. （不可能）Can it be t
10、rue? 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 home before eight oclock?-Yes, you mu
11、st. ( 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） must 表推测（一般用于肯定句）意为：一定 否定式： cantmu
12、st + V must + be doing must + have done eg: 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? （表现在状态，用have, has）3 must 和 have to4 will
13、 / 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wouldeg If 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. 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
14、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. (than do sth.) 3) would do (used to do)表示过去
15、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 对方意见或向对方请示。eg Shall 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 should
