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第二讲 语法- 情态动词

情态动词表示说话人的能力、义务、必要、猜测等语气或情感。情态动词必须和动词原形一起构成谓语，无人称和数的变化。其使用要点如下： 一、 情态动词考点解析

can, could和be able to的用法

1．can和could表示“能，会”，有一般现在时和一般过去时两种时态，在将来时和完成时中必须用be able to。表“能力”时can与be able to换用。 例如：Can you type? =Are you able to type?

We’ll be able to get you a job soon.（在将来时中不可用can） He has been able to finish the work on time.（在完成时中不可用can） 2． “can/could+ have done” 表“本能够做某事而没有做”。 例如：You could have been more careful. 你本能够更细心的。 3． “can’t/couldn’t+ have done”表“不可能做了某事”。 例如：Without your help, I can’t have made such great progress. 没有你的帮助，我不可能取得这么大的进步。 must和have to的用法

1．must和have to都表示“必须，不得不”。must强调主观性；have to强调客观需要。must只用于一般现在时，而have to有更多的时态形式。 例如：I must learn another language.（主观想法：我想要） I have to learn another language.（客观需要：我不得不） It’ll have to be finished in two days.（have to用于将来时中） He has had to reconsider his position.（have to用于现在完成时）

2．两者的否定意义不同：mustn’t表示“禁止；不可以”， 而don’t have to表示“不必”，意思相当needn’t。

例如：You mustn’t go. 你决不可以去。

You don’t have to go. 你不必去。

3．“must be +形容词或名词”表示对现在情况的肯定推测和判断；否定的推测用can’t。

例如：What he said must be true. 他说的一定是真的。 What he said can’t be true. 他说的不可能是真的。

This must be Jim’s pen. 这一定是吉姆的笔。

4．“must+have done”表示对过去情况的肯定推测；“can’t/couldn’t+have done”则表示对过去情况的否定推测。

例如：The ground is wet. It must have rained last night. 地面很湿，昨晚一定下过雨。

He can’t find his key. He must have left it in the car. 他找不到钥匙了一定是丢在车上了。

He can’t have finished the work in such a short time. 他不可能在这么短的时间内完成了这份工作。 should和ought to的用法

1．两者都表示“应该”，但should语气比ought to重，在日常交际中多用should，表一般的忠告。ought to 否定形式为ought not to。 You ought to respect the old. 你应该尊重老人。

You ought not to tell him about it. 你不应该告诉他那件事。

2． “should/ought to+have done ”表示“过去本应该做某事而没有做”；否定式“shouldn’t/ ought not to+have done”表“本不该做某事却做了”。 例如：I should have finished the work earlier. 我本应早点完成这项工作。

His wife is selfish. He oughtn’t to have married her. 他的妻子很自私，他本不该娶她的。 dare作情态动词和行为动词的用法

1．dare作情态动词主要用在否定句和疑问句中，其否定式是“dare not+动词原形”表“敢；竟敢”。

例如：She dare not speak in public. 她不敢在公众面前讲话。 How da re you do such a thing? 你怎敢做这样的事？

2．dare作为行为动词时，肯定式为“dare to do sth.”，to可以省略；其否定式为“don’t dare (to) do/ doesn’t dare (to) do/ didn’t dare (to) do”。

例如：She dares (to) swim in that river. 她敢于在那条河里游泳。 I don’t dare (to) speak of it. 我不敢说那件事。 need作情态动词和行为动词的用法

1. need作情态动词，常用于否定句和疑问句中，其否定式为“needn’t+动词原形”。 例如：You needn’t do anything here. 你在这里什么也不要做。 You needn’t go if you don’t want to. 你不想去就不必去。 You needn’t do it at once, need you? 你不必马上做，是吗？

2．need作行为动词，其否定式为“don’t need to do…”。后面接动词不定式，表主动；接动名词表被动。

例如：You don’t need to do it yourself. 你不必亲自做这件事。 I need to tell them the news. 我需要告诉他们这个消息。 This table needs painting.=This table needs to be painted. 这张桌子需要刷新。 情态动词的完成时和进行时 1．情态动词的完成时

must + have done（一定做了??） 推测过去情况的肯定发生了。 may/ might + have done（也许做了??）推测过去情况也许发生了。 can/could + have done（本能够做了??） 本能够做却没做。

can’t/ couldn’t + have done（不可能做了??） 推测过去情况不可能发生。 should/ ought to + have done（本该做了??） 过去本应该发生的而未发生。 shouldn’t / oughtn’t to + have done（本不该做了??） 过去本不应该发生的而发生了。

needn’t + have done（本不必做了??） 本不必做的事却做了。 2．情态动词的进行时

must be doing一定在做某事。 may be doing可能在做某事。 can’t be doing不可能在做某事。 shouldn’t be doing不应该在做某事

公外真题解析;

1.You___me because I didn’t say that. ( 2002-29 ) A. must misunderstand B. must be understanding C. must have understood D. had to misunderstand

2. Without his wise mother, he _____ such a successful scientist.

A. would not become B. should not have become C. may not have become D. could not have become 3. Go and get some water, _____?(2003)

A. don’t you B. shall you C. can’t you D. won’t you 4. I ___ a little earlier, but 1 met a friend of mine on the way. (2006-23)

A. should arrive B. would be arriving C. could have arrived D. arrived 5. I didn't see him at the meeting yesterday afternoon. He___it. (2006-42) A. mustn’t attend B. can ' t have attended C. wouldn’t have attended D. needn' t have attended 6. You ____ me because I didn’t say that.(2007) A. must understand B. must be understanding C. must have understood D. had to misunderstand

7. I'm not surprised you failed the exam. You ____have worked harder. (2008-21) A. should B. must C. would D. ought 8. You ___not have seen her yesterday, for she was abroad. (2009-12) A. must B. should C. could D. would 9. He must have stayed up late last night, ______he?(2011) A. mustn’t B. needn’t C. hasn’t D. didn’t

10. Let’s put the matter to the vote and not waste our time arguing about it, ______? (2012) A. shall we B. can we C. may I D. will you 11. I’m sorry that he _____ in such poor health.(2013) A. are B. shall be C. were D. should be 1-5 CDDCB 6-11CACDAD 专业情态动词真题：

1. If you ____ see Xiao Li in Beijing, please let him give me a call. A. would B. should C. will D. shall

2. This kind of work is hard and dangerous. But you would become rich ____. A. would you succeed B. ought you to succeed C. might you succeed D. should you succeed 3. Father said such a thing ____ to happen yesterday.