高中英语语法讲义——情态动词讲解（无答案）
展开情态动词
情态动词的定义：情态动词表示说话人的语气,愿望,态度和推测等，常见的情态动词（词组）有：can，could, may ,might, must, ought to, have to, shall, will, should, would, need, dare, be able to, had better等。
情态动词的特征：
1. 情态动词有一定的词义，但不完整，不能单独作谓语, 只能和其他动词原形构成谓语。
She may be the older of the two girls.
2.适用于主语的各种人称和数（have to例外，主语是第三人称时要用 has to）
We/He/You must work hard.
He has to walk home without a bike.
3.有些情态动词没有过去式，如must；有些有过去式。过去式用来表达更加客气, 委婉的语气, 时态性不强, 可用于过去，现在或将来。
can-could may-might will-would shall-should have to-had to
4.具有助动词的作用，即可帮助谓语动词构成否定句、疑问句。
I can’t swim. Can I open the window?
Ⅱ常见的情态动词的用法
1.can和 could的用法
情态动词 | 用法 | 例句 |
can和could
| 表示体力和脑力方面的能力，can表示现在的能力，could表示过去的能力 | He can get on well with his classmates. What he said yesterday afternoon could not be understood by anyone present. |
表示客观或理论上的可能性，意为“有时会，可能会” | Even an experienced teacher can make mistakes. It could be better to stay here. | |
表示请求和允许(could 此时比can更委婉、客气) | Can I use your portable computer this evening? Could I come here again tomorrow? | |
表示说话人的推测、怀疑、惊讶或不肯定等，主要用于否定句、疑问句或感叹句中(此时could比can语气弱) | He can’t be in the library. Can this be true? He couldn’t be playing basketball now. | |
can的习惯用法: cannot but do不得不（=have to do） | He cannot but choose to retire because of illness. |
2. must和have to的用法
情态动词 | 用法 | 例句 |
mmust
| 表示“必须，应该”，语气比should, ought to强烈，其否定形式mustn’t表示“不准，禁止” | You must come to school on time. You mustn’t waste any more time. |
在回答以must开头的一般疑问句时，否定回答常用needn’t或don’t have to,而不用 mustn’t | —Must I take part in the sports meeting? —Yes, you must./No, you needn’t (don’t have to).
| |
表示有把握的推测，意为“一定，准是，想必”，只用于肯定句中 | You must be hungry after a long walk. | |
have to | 表示“必须，不得不”，其意义与must相近。但must强调的是说话人的主观看法，而have to 则往往强调客观需要 | He had to work hard to support the family. In crowed places like airports and railway stations, you must take care of your luggage.
|
must只有一种形式，而have to则涉及人称、时态等方面的变化形式 | Tina had to turn down the invitation to the party last weekend because he was too busy. | |
mustn’t表示“禁止，不准”，don’t have to表示“不必”，相当于needn’t | You don’t have to buy a gift, but you can if you want to. |
- should和ought to的用法
情态动词 | 用法 | 例句 |
ought to和should | 表示说话者认为应该做 | He ought to be confident of victory. You should not attend the wedding ceremony. |
表示说话者根据一定的依据进行推测，常译为“按道理说应该” | She ought to pass her chemistry exam. Jack should be there by now. | |
needn’t 表示某一动作不必要做，而 ought not to表示某一动作是错误的，与shouldn’t类似，ought not to语气更强 | You ought not to use a dictionary for this exercise. |
Ⅲ 语法巩固：用适当的情态动词填空
1.—Oh, my God! You _________ wear slippers to attend the meeting.
—I’m sorry.
2. You’ll have plenty of time tomorrow, so you ________work too late tonight. But if you_______, I don’t have much to say.
3. —Could I come here again tomorrow?
—Yes, you _________.
- Looking people in the eye _________ sometimes make them stressful.
- Each student in our class__________ write two essays by Monday. It is our teacher’s order and we have no choice.
- You___________ use the office phone for personal calls. It’s not allowed.
- She__________ fry eggs when she was 8 years old.
- You__________ leave a baby alone in the office.
- You__________ leave the classroom during the test, as our teacher has announced this rule.
- Do be careful with electricity, for it is so dangerous. I think you __________ can an electrician.
Ⅳ语法选择
1. It is usually warm in my hometown in March, but it _________ be rather cold sometimes.
A. must B. can C. should D. would
2. The police still haven’t found the lost child, but they’re doing all they _______.
A. can B. may C. must D. should
3. It _______ be the postman at the door. It’s only six o’clock.
A. mustn’t B. can’t C. won’t D. needn’t
4. I _______ worry about my weekend— I always have my plans ready before it comes.
A. can’t B mustn’t C. daren’t D. needn’t
5. I have told you the truth. _______I keep repeating it?
A. Must B. Can C. May D. Will
6.—May I take this book out of the reading room？
—No, you ______. You should read it here.
A. mightn’t B. won’t C. needn’t D. mustn’t
7.—It’s the office! So you ______know eating is not allowed here.—Oh, sorry.
A. must B. will C. may D. need
8.—What sort of house do you want to have? Something big?
—Well, it _____be big—that’s not important.
A. mustn’t B. needn’t C. can’t D. won’t
9. In crowded places like airports and railway stations, you ______take care of your luggage.
A. can B. may C. must D. will
10.—What do you think we can do for our aged parents?
—You _____ do anything except to be with them and be yourself.
A. don’t have to B. oughtn’t to C. mustn’t D. can’t
