1 必修三unit2语法讲解情态动词用法（二） 、ought to的用法 1. ought 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” ①We ought to stop polluti ng n ature.我们应该停止污染大自然。 2. ought to表示较大的可能性。 ①Mary 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）。 3. ought to的否定形式为ought not to或ought n't to,其一般疑问句形式是将 ought置于主语前。 ①We 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ought n't或should n't。 ① He ought to take back what he has said, ought n' t/should n't he? 他应该收回他说的话，是吗？ 1 — 1.写出下面句中黑体部分的意义 ① To keep fit, weought to lear n more about our body. _____ ① Youought not to do such a thing. _______ ① Itought to be a close game. _______ 1 — 2.用ought完成句子 ①（尔不该责备他。You __________ （scold ）him. ①我明天该动身吗？ 一 _______________ （_leave ［tomorrow?

是的，你应该。一Yes, you ought to

①我们现在应该走，是吗？ We ought to go now, ______________ _? 二、have to, don't have to 与 must n't 的用法

1. have 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。 ① My brother was very ill, so I had to call the doctor in the middle of the ni ght. 我弟弟病了，我不得不半夜里把医生请来。 2

2. have to的否定式为don't have to,表示 没有义务或没有必要做某事 ”意 3

为“不必”，常可以回答 must 提问的一般疑问句 ① You don't 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：

⑴have to侧重客观需要,而must表示说话人的主观看法;

⑵have 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 must n't表示禁止” ① The magaz ines must n't be take n out of the read ing room. 不许把这些杂志拿出阅览室。 即学即练 2 2－1.用 have to 完成句子

I yesterday. They the nuclear radiation. ①我必须马上做吗？ —Must I do it at once?

不， 你不必。 —No, _________ ． 2－2.选词填空： must, mustn't, have to ①现在我不得不走了 ，因为我妈妈生病了 I __________ go now, for my mother is ill. ①我一定要戒烟。 I ______ stop smoking. ①晚上你一定不能独自出去。 You __________ go out alone at night. ①湖南高考)You _________ buy a gift, but you can if you want to. A．must B．mustn't C．have to D．don't have to 三、need的用法

1．need 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。

①You n eed n't come so ear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、 数的变化 ，构成否定句和疑问句时要借助于助动词 do 或 does。

① We don't 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。 3— 1.用need或must完成句子

①你现在不必去那儿。You needn't go there now. ①他有必要留在这儿吗？ 一 Need he stay here?

是的，他必须。/不，他不必要。一Yes, he must /No, he needn't

①天色太晚了 ，我现在得回家了 It's too late, so I now.

①昨天我不得不离开。 ①他们没有必要担心核辐射。 4

①天津高考）It's quite warm here; we ________ turn the heating on yet. A. could n't B. must n't C. need n't D. would n't 四、情态动词+ have done的用法

1. must have done用于肯定句,表示过去一定做过某事”。 ① How can you be late aga in? You must have overslept. 你怎么又迟到了？你一定是睡过头了。

2. can/could have done—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”。 ① He can' t/could n't have watched TV last ni ght, 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了。 ① We could have arrived there before dark, but we did n't. 天黑前我们本来能够到那里的，但是没到。

3. should/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。 ① 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。

4. may/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”，多用在肯定句中，用might时表示语气更加不肯 ^定。 ① 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。 5. need n't have done表示 本不必做某事而实际做了 ”。 ① He is old eno ugh! You n eed n't have solved the problem for him. 他够大了！你根本没必要为他解决问题。

4—1.根据汉语意义，用 情态动词+ have done”填空 ①你肯定看过电影《归来》。 You _________________ the film Comi ng Home.

①史密斯先生不可能去北京了 ，我刚才还在图书馆看见他。 5

Mr.Smith _____________to Beiji ng, for I saw him in the library just now. ①本来他能够通过考试，但是他太粗心了。 He _______________ the exam, but he was too careless. ①以前你应该多进行锻炼的。 You ______________ more exercise before. ①你可能已经在报上看过这个消息。 You ______________ about it in the papers.

①你本不必告诉我这个消息，我已经知道了。 You ______________ me the n ews .I have already known it. ①四川高考)—Why are your eyes so red? You ______ have slept well last night. —Yeah, I stayed up late writ ing a report. A. can't B. must n't C. need n't D. won't

①浙江高考)1 ______ myself more — it was a perfect day. A. should n't have enjoyed B. need n't have enjoyed C. would n't have enjoyed D. could n't have enjo yed ①陕西高考)The children _________ lost in the woods; otherwise, they would have bee n at the lakeside camp as scheduled. A. must have got B. must get C . should have got D . should get ①江西高考)We ____ have bought so much food now that Suzie won't be with us for dinner. A. may not B . n eed n't C . can't D . must n't

①选词填空 1 . You ________ go there alone; it's too dangerous. (mustn't/needn't) 2 . It's so n ear; we ________ have take n a taxi.(should n't/ca n't) 3 . You ___________ have spent so much time playing com-puter games.(must n't/ought n't to) 4. — Shall I leave the room so that you two can talk? —No, you _________ . (must n't/n eed n't) 5 . He _______ have missed the train; he arrived at the train stati on two hours early.(ca n't/must n't) 6 . We'll be very glad if you _________ oin us in going camp in g.(ca n/may) 7 . They __ stay in the office last ni ght because of the sno wstorm.(have to/must) 8 . We ______ have helped him; in that case, he would have bee n able to finish the work.(should/ca n)