复习回顾
情态动词表示说话人对某一动作或状态的态度。初中阶段大家已经学习了一些情态动词，这里将对情态动词的特征、功能和用法进行总结。
[观察例句]
1．Oliver believes that with a millionpound bank note a man could live a month in London.
2．Young man，would you step inside a moment，please?
3．May we ask what you’re doing in this country and what your plans are?
4．I can’t say that I have any plans.
5．Anyway，I didn’t dare to try again.
6．You mustn’t worry about that.
7．If you’ll excuse me，I ought to be on my way.
[归纳用法]
1．情态动词的基本特征
(1)在形式上，情态动词没有实义动词的各种变化，只有could，would，had to，might等几个过去式，其他情态动词如must、ought to等的过去式皆与现在式同形。
(2)在意义上，大多数情态动词有多个意义，如can可以表达“能力；可能；许可”等。
(3)在用法上，情态动词与助动词一样，需后接动词原形，构成谓语动词。
2．情态动词的否定式及缩略形式
| 情态动词 | 否定式 | 缩略形式 | 情态动词 | 否定式 | 缩略形式 |
| can | cannot/ can not | can’t | shall | shall not | shan’t |
| could | could not | couldn’t | could | should not | shouldn’t |
| may | may not | / | will | will not | won’t |
| might | might not | mightn’t | would | would not | wouldn’t |
| must | must not | mustn’t | need | need not | needn’t |
| dare | dare not | daren’t | ought to | ought not to | oughtn’t to |
主要表意功能
| 用法 | 例句 |
| 表示能力 | The little boy can read and write. I could feel the ground shaking. |
| 表示可能和推测 | Those of you who are familiar with the game will know this. They made a bet which would settle their argument. Oh，you must be Sylvia’s husband. It may seem lucky to you but not to me. That might not be true. There ought to be enough space for all of us. |
| 表示许可或禁止 | You can go off duty now. You can’t open it until two o’clock. You may not smoke here. You shouldn’t take her help for granted. You mustn’t do that. |
| 表示发出指示或提出请求 | Will you please take her to the library? Could you offer me work here? Can I ask a question? May we ask what you’re doing in this country？ |
| 表示提出帮助或发出邀请 | Will you stay for lunch? Wouldn’t you like to come with me? May I help you? Shall I put it in a box？ |
| 表示提出建议 | You could ask the teacher for help. You should write him a letter. The cookies Susan made are delicious ，you ought to try some. |
| 表示愿望 | Would you recommend the play to other people? I would like to know the date. I’d love to go to your birthday party. I’d rather not pay you now. |
| 表示义务和需要 | You must come at once. We have to wear uniforms at school. I ought to be on my way. |
难点透视
英语中的情态动词虽然为数不多，但是要掌握好它们的用法并不容易。下面结合同学们在使用情态动词时不易掌握的难点谈几点看法。
(1)①can表示可能性时，指的是理论上的可能，它通常不用来表示某事实际发生的可能性或真实性。如：Accidents can happen. Anybody can make mistakes.
如果我们要表达某事发生的实际可能性，要用may，could或might等。
We may spend our summer holidays in Hangzhou this year.
Will you answer the telephone？It could/may/might be your mother.
②could用来征求意见时，语气要比can委婉，但在回答问题时我们不能用could，因为语气委婉，可能性就变小了。如：
—Could I use your telephone?
—Yes，please go ahead.
③在过去时态的肯定句中需要某种条件或努力做成某事，我们要用was/were able to而不能用could。如：
It was a holiday and the children were able to go to the seaside.
The girl worked hard so she was able to pass the final test.
(2)must与have to都可以表示“必须”的意思，但要注意以下两点区别。
①must只有现在时，而have to有现在时、过去时和将来时。如：
We must work hard，or we’ll fail in the examination.
Years ago，the poor girl had to leave school for lack of money.
②must表示主观看法，have to则侧重于客观需要。如：
We must be strict with ourselves in everything.
In cities with many cars，some people have to wear masks.
(3)shall可以用来征求对方意见，用于第一、三人称。此外它也可以用来表示说话人的命令、警告、允诺、威胁或决心等，这时它用于第二、三人称。如：
Shall she go to the concert with us this evening？(征求意见)
You shall go to the front at once.(命令)
Don’t worry.You shall get the answer this very afternoon.(允诺)
He shall be sorry one day.I tell you.(警告)
Nothing shall stop us from fighting against pollution.(决心)
(4)在表示将来的时间、条件状语从句中，不能用will(这时的will不是情态动词，而是助动词，帮助构成将来时)。如：
If it will rain tomorrow，we shall not go to the mountain village.(误)
If it rains tomorrow，we shall not go to the mountain village.(正)
当情态动词will表示意愿或决心时，是可以用于条件状语从句的。如：
If you will listen to me，I’ll give you some advice on how to learn English.
If you will come this way，the manager will meet you.
(5)should除表示必要或义务外，还可表示推测或可能。如：
The American friends should be here now.
(6)ought to与should意思接近，大多数情况下二者可以互换，但是should谈的是自己的主观看法，ought to则更多反映客观情况，在谈到法律、义务和规定时使用。如：
We should/ought to help each other and learn from each other in our work.
She is your mother，so you ought to support her.
We ought to go and see Mary tomorrow，but I don’t think we will.
(7)dare与need的用法
①dare作为情态动词，主要用于疑问句、否定句和条件从句中，一般不用于肯定句。
a．How dare you say I’m unfair?
b．He daren’t speak English before such a crowd，dare he?
c．If he dare break the rule，he will be punished.
②need表示“需要”或“必须”，作情态动词用时，仅用于否定句或疑问句、条件从句中。意为“有……必要”。在肯定句中一般用must，have to，ought to或should代替。
a．You needn’t come so early.
b．—Need I finish the work today?
—Yes，you must./No，you needn’t.
c．If you need go there，please let me know.
d. We must/need to report the matter to the boss immediately.
③dare和need常用作实义动词，有时态、人称和数的变化。所不同的是，在肯定句中，dare后面通常接带to的不定式；在否定和疑问句中，dare后可接带to或不带to的不定式。
a．I dare to swim across the river.
b．He doesn’t dare(to)answer.
c．We need time and money.
d．The dining room needs/wants/requires cleaning every day. (主动表被动的用法)
＝The dining room needs/wants/requires to be cleaned every day.
e．Does he need to take the medicine three times a day?
重点-表推测
1、对现在或将来的推测：must 肯定、can’t/couldn’t 不可能、may/might 可能；（could/might不表示过去，只是相对于can/may，语气更弱一些。）
The mathematics teacher must be in the office now.
There is no light in the room. She can’t be at home now.
If I’m busy, I may not go.
2、对现在进行情况的推测：must 肯定、can’t不可能、may 可能 + be doing
The girl is not out. She must be doing her homework now.
He may be waiting for you at the cinema.
Ling Ling can’t be playing the piano now. She went to the bookshop with her father a few minutes ago.
3、对过去的推测
（1）“must＋have＋done”用来表示“肯定已经做了…”。
The children must have watered the tomatoes yesterday.
The minister must have arrived in Shanghai.
I must have forgotten to tell you.
（2）“should/ought to＋have＋done” 表示”本该做，而实际上却没有做的事“，含有责怪的意思；用于否定句”shouldn’t/ought not to＋have＋done”中，表示”本来不该做，但实际上做了“，也是含有责怪的意思。
You should have told her about it the day before yesterday.
You shouldn’t have told such a lie.
（3）“may/might＋have＋done”表示“或许已经…”；“may/might not＋have＋done”表示“或许还没有…”
It’s too late. I think he may have gone to bed.
He may not have gone home. He might have gone somewhere else.
（4）“can/could＋have＋done”多用于问句、否定句中，表示“可能（已经）…吗”、“不可能（已经）…了”；用于肯定句中，表示“本来可以…的，（但实际上却没有），含有轻微的责怪。
—Could she have heard of him? —Yes, she must have heard of him.
He couldn’t possibly have said why. 他肯定说不出个所以然来。
You could have done better, but you were too careless.
（5）“needn’t＋have＋done”表示“本来可以不必…的（可实际上却已经…了）”。
You needn’t have taken a taxi here, for it was very near to my house.
You needn’t have woken him up at 5 o’clock. It’s too early.
高频短语表达
1、can but 有“只能,只好,至多不过”之意。
I don’t think we’ll succeed. Still, we can but try. 我想我们不会成功，但是不妨试一试。
With no key on him,he can but wait outside the door. 他没带钥匙，只好在门外等。
2、cannot help but 不得不,后接动词原形。
Due to the present price level,we cannot help but adjust our offer. 由于目前的价格水平，我们不得不调整报价。
3、cannot help意为“不禁，禁不住”，后跟名词、代词、doing 或 one’s doing
I cannot help missing that girl.我禁不住思念那个女孩。
4、cannot…too…表示“无论怎样……都不过分”,“越……越好”。有时 cannot 可用 can never 替代。
We cannot urge upon you too strongly the importance of this matter. 对此事，我们无论怎样向你强调其重要性都不会过分。
You can never be too careful when crossing the street.你过马路时怎么小心也不过分。
注意事项
①表示猜测，can一般不用于肯定句中，除非是“经验之谈”。这时can可以表示客观的可能性，并不牵涉具体的事情是否会发生；要表示某事发生的可能性时需要用could，may，might。
Children can often get ill suddenly.
Certain things in the home can be dangerous，especially if you have young children.
上面两句可以看作医务工作者或抚养过孩子的人说的话，属“经验之谈”。
②may和might表可能性的推测时都不用于疑问句中。如：
Can/Could it be cloudy tomorrow？(正)
May/Might it be cloudy tomorrow？(误)
③must表肯定推测时的否定式是can’t/couldn’t，不是needn’t或mustn’t。
④should/ought to＋动词原形：想必现在/将来会……
The dinner should/ought to be ready now.
He should/ought to ring up this afternoon.
⑤will＋动词原形：将来一定/准会……
Try your best，and your wish will come true.
Mindmap解析
Exercises
一、完成句子
1．我们必须努力学习，否则就不会通过考试。We _____________________，or we’ll fail in the examination.
2．这个女孩非常用功，所以她通过了最终的考试。
The girl worked hard so she _____________________________ the final examination.
3．你怎么能捉弄我呢？How can you _____________________________ on me?
4．——我们今天必须把这些玩具分类完毕吗？——不，你们不必。
—Must we sort these toys today? —No，_____________________________
5．我们应当尊重我们的老师和父母。We _____________________________ our teachers and parents.
二、用适当的情态动词填空
1．—Can’t you stay a little longer?
—It’s getting late. I really __________ go now. My daughter is at home alone.
2．—Shall I inform him of the change of the schedule right now?
—I am afraid you __________，in case he comes late for the meeting.
3．He _______ sleep，although he tried to，when he got on such a hunt for an idea until he had caught it.
4．You __________ park here！It’s an emergency exit.
5．Doctors say that exercise is important for health，but it __________ be regular exercise.
6．The police still haven’t found the lost child，but they’re doing all they __________．
7．—Why are your eyes so red？You __________ have slept well last night.
—Yeah，I stayed up late writing a report.
8．According to the newlymade traffic regulation，whoever drives through red lights __________ be fined at least 200 dollars.
9．George__________ have gone too far.His coffee is still warm.
10．You __________ be Carol.You haven’t changed a bit after all these years.
三、短文语法填空
A long time ago，there was a woman，1. __________ had two children. One was called Tom，and the other was named John. One day the woman was very puzzled(疑惑的)．She had some cakes in the kitchen but every night one of her children 2. __________ eat them. She thought it 3. __________ be Tom because he was very tall 4. __________ John was very short. But she wasn’t sure. The woman had an idea. She put the cakes on a high shelf. The next day，someone 5. __________ (eat) some of the cakes. “Ah！”said the woman.“It 6. __________ be John. He’s too short！It 7. __________ be Tom！”She was very angry with Tom，8. __________ (think)，“He 9. __________ be punished for what he had done！”Poor Tom. In fact，he hadn’t eaten the cakes. It was John. How？Can you guess？Yes，he 10. __________ have used a chair!
KEYS：
KEYS：
一、完成句子
1．We must work hard，
2． she was able to pass the final examination.
3．How can you play a trick on me?
4． —No，you needn’t/don’t have to．
5．We should respect our teachers and parents.
二、用适当的情态动词填空
1． I really must go now.
2．—I am afraid you must，
3．He couldn’t sleep，
4．You mustn’t park here！
5． but it must be regular exercise.
6． but they’re doing all they can．
7． You can’t have slept well last night.
8． shall be fined at least 200 dollars.
9．George can’t have gone too far.
10．You must be Carol.
三、短文语法填空
1.who 2.would 3.might 4.while 5.ate(eat) 6.can’t 7.must 9.shall 10.must