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1、精选优质文档-倾情为你奉上必修三unit2语法讲解情态动词用法（二）一、ought to的用法1ought to“应该”。与should相比较ought to语气重，偏重“责任、义务、道德、法律”等方面，意为“应该”。We ought to stop polluting nature. 我们应该停止污染大自然。2ought to 表示较大的可能性。Mary ought to be here soon. 玛丽应该很快就来了。点津用ought to表示推断时，语气较肯定，通常指的是一种合乎逻辑的可能性(与should表推断时相似)，有时可译为“很可能；准是”(语气比must要弱)。3ought t
2、o的否定形式为ought not to 或oughtnt to, 其一般疑问句形式是将ought置于主语前。We ought not to start so late. 我们不该这么晚动身。4在反意疑问句中，常省掉to用oughtnt或shouldnt。He ought to take back what he has said, oughtnt/shouldnt he?他应该收回他说的话，是吗？11.写出下面句中黑体部分的意义To keep fit, we ought to learn more about our body._You ought not to do such a thing
3、._ It ought to be a close game._12.用ought完成句子你不该责备他。You _(scold )him.我明天该动身吗？_(_leave )tomorrow?是的，你应该。Yes, you_ought_to我们现在应该走，是吗？ We ought to go now, _?二、have to, dont have to与mustnt的用法1have to(口语中常用have got to)表示客观需要做的事情，意为“必须；不得不”。有时态、人称和数的变化，其否定式和疑问式应由助动词do构成。My brother was very ill, so I had t
4、o call the doctor in the middle of the night.我弟弟病了，我不得不半夜里把医生请来。2have to的否定式为dont have to，表示“没有义务或没有必要做某事”，意为“不必”，常可以回答must提问的一般疑问句。You dont have to finish the work now.你现在没有必要完成这项工作。辨析比较must和have to都有“必须”之意，但二者有区别：(1)have to侧重客观需要，而must表示说话人的主观看法；(2)have to有时态、人称和数的变化，而must只有一种形式；(3)must的否定式mustnt
5、表示“禁止”。The magazines mustnt be taken out of the reading room.不许把这些杂志拿出阅览室。即学即练221.用have to完成句子天色太晚了，我现在得回家了。 Its too late, so I _ now. 昨天我不得不离开。 I _ yesterday.他们没有必要担心核辐射。 They _the nuclear radiation.我必须马上做吗？Must I do it at once?不，你不必。No, _22.选词填空：must, mustnt, have to现在我不得不走了，因为我妈妈生病了。I _ go now, f
6、or my mother is ill.我一定要戒烟。 I_ stop smoking.晚上你一定不能独自出去。 You _go out alone at night.(湖南高考)You _ buy a gift, but you can if you want to.AmustBmustnt Chave to Ddont have to三、need的用法1need 作情态动词时，后跟动词原形，表示“需要；有必要”，无人称和数的变化，多用于否定句、疑问句或条件句中。You neednt come so early.你不必来这么早。2作为实义动词，同其他实义动词一样，可用于各种句式，有时态、人称
7、、数的变化，构成否定句和疑问句时要借助于助动词do或does。We dont need to spend more time on it.我们没有必要在这个事情上花太多的时间。31.用need或must完成句子你现在不必去那儿。You neednt go there now.他有必要留在这儿吗？Need he stay here?是的，他必须。/不，他不必要。Yes, he must/No, he neednt(天津高考)Its quite warm here; we _ turn the heating on yet.Acouldnt Bmustnt Cneednt Dwouldnt四、情态
8、动词have done的用法1must have done 用于肯定句，表示“过去一定做过某事”。How can you be late again? You must have overslept.你怎么又迟到了？你一定是睡过头了。2can/could have done一般用于疑问句和否定句中，表示对过去所发生事情的推测。could have done用于肯定句时，表示“本有能力做某事而未做”。He cant/couldnt have watched TV last night, for he knew he would have a test. 昨天晚上他不可能看电视，因为他知道就要考试
9、了。We could have arrived there before dark, but we didnt.天黑前我们本来能够到那里的，但是没到。3should/ought to have done 表示“过去本应该做某事而(实际上)没有做”，含有责备或遗憾的语气；其否定形式表示某种行为不该发生却发生了。You should have told me earlier or I might have gone with them.你应该早点告诉我，不然的话我就会和他们一块去了。4may/might have done 表示对过去发生的事情的推测，意为“也许已经做了某事，可能已经做了某事”，多
10、用在肯定句中，用might时表示语气更加不肯定。If you had studied hard, you might have passed the exam.如果你努力学习的话，你可能会及格的。5neednt have done表示“本不必做某事而实际做了”。He is old enough! You neednt have solved the problem for him.他够大了！你根本没必要为他解决问题。41.根据汉语意义，用“情态动词have done”填空你肯定看过电影归来。You_ the film Coming Home.史密斯先生不可能去北京了，我刚才还在图书馆看见他。M
11、r.Smith _ to Beijing, for I saw him in the library just now.本来他能够通过考试，但是他太粗心了。He _the exam, but he was too careless.以前你应该多进行锻炼的。You _more exercise before.你可能已经在报上看过这个消息。You _ about it in the papers.你本不必告诉我这个消息，我已经知道了。You _ me the news.I have already known it.(四川高考)Why are your eyes so red? You _ hav
12、e slept well last night.Yeah, I stayed up late writing a report.AcantBmustnt Cneednt Dwont(浙江高考)I _ myself more it was a perfect day.Ashouldnt have enjoyed Bneednt have enjoyedCwouldnt have enjoyed Dcouldnt have enjoyed(陕西高考)The children _ lost in the woods; otherwise, they would have been at the la
13、keside camp as scheduled.Amust have got Bmust get Cshould have got Dshould get(江西高考)We _ have bought so much food now that Suzie wont be with us for dinner.Amay not Bneednt Ccant Dmustnt .选词填空1You _go there alone; its too dangerous. (mustnt/neednt)2Its so near; we _ have taken a taxi.(shouldnt/cant)
14、3You _ have spent so much time playing computer games.(mustnt/oughtnt to)4Shall I leave the room so that you two can talk?No, you _. (mustnt/neednt)5He _ have missed the train; he arrived at the train station two hours early.(cant/mustnt)6Well be very glad if you _join us in going camping.(can/may)7They_stay in the office last night because of the snowstorm.(have to/must) 8We _ have helped him; in that case, he would have been able to finish the work.(should/can)专心-专注-专业