1、情态动词专题讲解一情态动词(Model Verbs)的语法特征情态动词主要有 can, may, must, could, might, shall , should, will, would, ought to, need, dare 等。1） 情态动词不能表示正在发生或已经发生的事情，只表示期待或估计某事的发生。2） 情态动词 除 ought 和 have 外，后面只能接不带 to 的不定式,即动词原形。3） 情态动词没有人称，数的变化，即情态动词第三人称单数不加-s 。4） 情态动词没有非谓语形式，即没有不定式，分词等形式。二. 情态动词的基本用法1) can、could 和 be ab
2、le to can 和 be able to 都表示能力(Ability)，意思上没多大区别。但 can 只有现在和过去时，而 be able to 则有更多的形式。但当成功地完成某一具体动作时，通常不用could 而用 was/were able to 来表示。这时 was/were able to 表示经过一番努力，终于能够完成某事, 在许多情况下又可以交替使用。如：Can you use chopsticks?I cant do it now, but I can do it later.Is there anything I can do for you.The wounded man
3、 still was able to get to the village and was saved in the end.As I have got enough money, I can / am able to help her.can 和 couldcan 和 could 都可以表示能力、技能、许可、建议或请求和可能性。但比较委婉客气地提出问题或陈述看法，一般用 could，回答时则用 can。但在肯定句中， could 所表示的“能力”仅是泛指过去的一般能力。如：Could you help me carry the bag?She could play the piano whe
4、n she was only six.Can I help you?在疑问句表示“可能”， 须用 can 而不用 may。如：Where can he be? He may be in the office.Can they have missed the bus? Yes, they may have.2) must 和 have to must 和 have to 都可以表示“ 必须”，但有几点区别： must 强调“内在的职责”、“ 义务”，而 have to 强调“ 外界压力”、“不得已而为之”。 have to 可用于多种时态，而 must 一般用于现在时，其过去时与将来时分别由ha
5、d to 与 shall / will have to 代替。 在回答 must 引起的问题时，如果是否定的答复，不能用 mustnt，而要用neednt 或 dont have to，因为 mustnt 是“一定不要” 、“一定不能”的意思。如： You must come to the classroom before eight. It is raining hard outside, but I have to leave now. “Must we do it now?” “No, you neednt.” 3） shallshall 作为情态动词用于第二、三人称，表示说话人的意愿，
6、有“命令” 、“警告、威胁、强制” 和“ 允许”等意思。如：We shall do as our teacher says.You shall have the book as soon as I finish it.在疑问句中，shall 用于征求对方的意见或请求指示，常用于第一、第三人称。如： Where shall he wait for us? / Shall we go out for a walk? 4) need 的用法need 既可用作情态动词，也可用作行为动词，作“必须”、“需要”讲。作为情态动词，need 也只用于否定句和疑问句。如：He neednt worry abou
7、t it.Need I collect the books myself?作为行为动词，其后接的不定式要加 to。如:I want to go to the dentist, but you need not go with me我要去看牙科医生，但你不必跟我一起去。( need 作情态动词)He needs to buy a new pair of shoes.他需要买一双新鞋子。(need 作实义动词)以 need 作情态动词提问，其答语如果是肯定的，须用 must; 如果答语是否定的，则用 neednt。如：Need we work late today? No, but we must
8、 tomorrow.Need I tell Tome at once? No, you neednt tell her just yet.三. 情态动词表示推测或判断的用法1） 情态动词+动词原形: 表示对现在或将来的情况的推测，此时动词通常为系动词。如:At this moment, our teacher must be correcting our exam papers.You must be hungry after a long walk.She may not be at home. = It is possible that she is not at home.She can
9、t be at home. = It is impossible that she is at home.They should be there right now.2） 情态动词+动词完成时, 即“ 情态动词+ have + done 分词”:表示对过去行为或动作进行推测、评论或判断。must have done 表示对过去某事的肯定猜测（只用于肯定句）“一定已做 ” cant /couldnt have done 表示对过去的否定推测. “不可能已做” (can/could have done 表推测通常只用于否定句和疑问句)may /might have done 表示对过去的可能推测
10、 “可能已做 ”（ may 比 might 表示的可能性在说话人看来稍大些。）如: Since the road is wet, it must have rained last night. He cant have missed the way. I drew him a map. “The dictionary has disappeared. Who could have taken it?” I cant find my keys. I may / might have left them at the school yesterday.四、情态动词在虚拟语气中的用法情态动词用于虚拟
11、语气中表示责备的感情色彩，用法如下：1）should have done 表示“本来应该做某事而实际上未做 ”，而 shouldnt have done 则表示“本不应该做某事而实际上做了” 。如： You should have told me about it earlier.You shouldnt have said such words to your parents.2) ought to have done 也表示“本应该”而 ought not to have done 则意为“ 本不应该”。如： You ought to have told me about it earli
12、er.You ought not to have said such words to your parents.3）neednt have done 表示 “本无必要做某事而实际上做了”。如： You neednt have walked so quickly since time was enough.4）could have done 表示“本来有可能而事实上未做到” 。如： I could have come on time, but my car broke on the way.情态动词专项训练1) I hear youve got a set of valuable Austra
13、lian coins _ I have a lookYes, certainly ADo BMay C. Shall DShould2) Mr Bush is on time for everything How _it be that he was late for the opening ceremony? Acan B should Cmay Dmust 3) Are you coming to Jeffs partyIm not sure I _ go to the concert instead A. must B. would Cshould Dmight 4) Johnny, y
14、ou _play with the knife, you _ hurt yourself Awont; cant Bmustnt; may Cshouldnt; must Dcant; shouldnt 5) Could I borrow your dictionaryYes, of course you _ Amight Bwill Ccan Dshould 6) The fire spread through the hotel very quickly but everyone _ get out Ahad to Bwould Ccould Dwas able to7) Shall I
15、tell John about it No, you _Ive told him already A. neednt Bwouldnt Cmustnt D. shouldnt 8) He_ his parents about his failure in the examination.A. dares not tell B. dare not tellingC. dare not tell D. dare not to tell9) At last she left her house and got to the airport, only _the plane flying away.A
16、. to see B. saw C. to have seen D. having seen10) He_ be in the classroom, I think.No, he _ be in the classroom. I saw him go home a minute ago. A. can; may not B. must; may not C. may; cant D. may; mustnt11). Must I do my homework at once?No, you_. A. neednt B. mustnt C. cant D. may not12). _ I tak
17、e the newspaper away?No, you mustnt. You _read it only here.A. Must; can B. May; can C. Need; must D. Must; must13). _ you like to have another try?A. Could B. Will C. Would D. Do14). You_ all those clothes! We have a washing machine to do that sort of thingA. neednt have washed B. shouldnt have was
18、hed C. must not have washed D. can not have washed15) The room is in a terrible mess; it _cleaned. A. cant have been B. shouldnt have been C. mustnt have been D. wouldnt have been16) Nobody knows how people first came to these islands. They _ from South America on rafts.A. must have sailed B. can sa
19、il C. might have sailed D. should have sailed17) Bob stop trying when he _the next time.A. can have succeeded B. will have succeededC. might have succeeded D. should have succeeded18). You_ to town to see the film yesterday. It will be on TV tonight.A. neednt go B. had better not go C. should not go
20、 D. neednt have gone19) .We_ the letter yesterday, but it didnt arrive.A. must receive B. ought to receive C. must have received D. ought to have received20) .I am feeling sick. I_ so much chocolate.A. neednt have eaten B. couldnt have eaten C. mustnt have eaten D. shouldnt have eaten21) I didnt sen
21、d out my application form last week, but I _.A. had B. would do C. should have D. might have to22) .You should bear in mind that he is not so strong as he_.A. was used to be B. used to be C. was used to D. use to23) Mary _my letter, otherwise she would have replied before now.A. should have received
22、 B. has receivedC. Couldnt have received D. ought to have received24)“Where _ my umbrella?” “Somebody _ it away by mistake.”A. is, must have taken B. is, must take C. have been, must take D. is, takes25) You _ your tooth pulled out before it rot completely.A. had better got B. had to get better C. had better to get D. had better get26) Susan must_ quite well in the exam since she seems so confident of passing the text.A. do B. be doing C. have done D. must have been dong
