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中小学教育资源及组卷应用平台
Unit 2 Home Sweet Home 单元语法讲练
情态动词can和could
一、 基本含义和用法
1. 表示能力 (Ability)
can： 表示现在或一般性的能力。
I can speak a little English. (我现在能说一点英语。)
She can swim very well. (她游泳游得很好。)
could： 表示过去的能力。
When I was young, I could run very fast. (我年轻时跑得很快。)
He could read when he was four. (他四岁时就能阅读了。)
注意： 表示过去某种具体场合成功做到了某事，通常用 was/were able to 或 managed to， 而不用 could。
The fire was big, but everyone was able to escape. (火势很大，但大家都成功逃生了。)
2. 表示请求和许可 (Requests and Permission)
Can I/Could I... ： 用于请求许可，意为“我可以...吗？”。Could 比 Can 更加礼貌和正式。
Can I use your pen (非正式、随意)
Could I borrow your dictionary (更礼貌、正式)
Can you/Could you... ： 用于请求别人做某事，意为“你能...吗？”。同样，Could you 比 Can you 更客气。
Can you help me with my homework
Could you pass me the salt, please (非常常见的餐桌用语)
表示给予许可时，通常用 can， 而不用 could。
— Could I leave early today — Yes, you can. (—我今天能早点走吗？—可以。)
3. 表示可能性 (Possibility)
can： 表示理论上的或泛指的的可能性（即某事可能发生，但不一定在特定时间），常用于肯定句。
It can be very cold in winter here. (这儿的冬天有时会很冷。)
Smoking can cause cancer. (吸烟可能致癌。)
could： 表示现在的可能性，但语气比 can 更不确定；也可以表示过去的可能性。
— Where is John — He could be in the library. (—约翰在哪？—他可能在图书馆吧。)(不太确定)
It could rain later. (待会儿可能会下雨。)
Yesterday, he could have been at home. (昨天他可能在家来着。)(过去可能性)
4. 表示推测 (Guessing)
can’t / couldn’t： 表示有把握的否定推测，意为“不可能”。
That can’t be true! (那不可能是真的！)
He couldn’t have stolen the money because he wasn’t there. (他不可能偷了钱，因为他当时不在那儿。)
can 一般不用于肯定句的推测。肯定推测用 must, may, might。
(正) He must be at home. The light is on. (他一定在家。灯亮着。)
(误) He can be at home.
5. could 的特殊用法：提出建议或提供选择
You could...： 可以用来委婉地提出建议。
If you’re tired, you could go to bed early. (如果你累了，可以早点睡觉。)
— I need to go to the station. — You could take a bus. (—我得去车站。—你可以坐公交车。)
6. can 和 could 与感官动词
当表示某人/某物具有某种特性时，can 常与 see, hear, smell, taste, feel 等感官动词连用。
I can see a bird in the tree. (我能看见树上有只鸟。)
This soup tastes good. (这汤尝起来不错。) → I can taste the pepper in the soup. (我能尝出汤里的胡椒味。)
巩固练习 (50题)
I. 单项选择
1. I ________ swim when I was five years old.
A. can B. could C. may D. must
2. — ________ you help me with this heavy box
— Sure, no problem.
A. Could B. May C. Must D. Shall
3. It ________ be very windy on the top of the mountain. Take a jacket.
A. can B. must C. should D. would
4. That man ________ be Mr. Li. Mr. Li is much taller.
A. mustn’t B. can’t C. shouldn’t D. wouldn’t
5. — ________ I ask you a question, Mr. Wang
— Of course, you ________.
A. Could; can B. Can; could C. May; may D. Could; could
6. My brother ________ play the guitar very well now.
A. can B. could C. was able to D. will can
7. The phone is ringing. Who ________ it be
A. can B. must C. may D. should
8. I ________ hear you clearly. Could you please speak a little louder
A. can’t B. couldn’t C. mustn’t D. shouldn’t
9. — I need to go to the post office.
— You ________ take Bus No. 103.
A. can B. could C. either A or B D. must
10. She practiced hard and finally ________ win the competition.
A. can B. could C. is able to D. was able to
11. — Look! Someone is coming. Who ________ it be
— It ________ be our teacher. She is in her office.
A. can; mustn’t B. can; can’t C. must; can D. may; must
12. ________ you play the piano for us at the party next week
A. Can B. Could C. May D. Might
13. — Mum, ________ I go to the movies with Lisa tonight
— Yes, but you ________ finish your homework first.
A. could; can B. can; could C. may; can D. can; must
14. I ________ understand what he said because he spoke too fast.
A. can’t B. couldn’t C. mustn’t D. shouldn’t
15. — I didn’t see you at the meeting yesterday.
— I ________ come because I was sick.
A. can’t B. couldn’t C. mustn’t D. shouldn’t
16. The story ________ be true. It sounds unbelievable.
A. might not B. couldn’t C. can’t D. may not
17. — ________ I use your bathroom
— Yes, of course.
A. May B. Must C. Need D. Should
18. He ________ run a mile in under four minutes when he was in college.
A. can B. could C. may D. might
19. — What ________ I get for your birthday
— You ________ get me a book.
A. can; could B. could; can C. should; can D. can; can
20. — Why didn’t you answer my phone
— I ________ hear it. I was listening to music.
A. can’t B. couldn’t C. mustn’t D. shouldn’t
II. 用 can, could, can’t, couldn’t, was able to 填空
21. My grandfather is over eighty, but he ________ still read without glasses.
22. I’m sorry I ________ come to your party last Saturday.
23. The fire spread quickly, but everyone ________ escape.
24. ________ you ride a bike when you were seven
25. It’s so dark. I ________ see anything.
26. — ________ you speak French — No, I ________.
27. She said she ________ help me with my project.
28. He ________ be over sixty. He looks so young!
29. We ________ hear the music from the open window.
30. I tried my best, but I ________ solve the problem.
III. 句型转换（按要求改写句子）
31. I was able to solve the math problem. (用 could 替换)
→ I ________ ________ the math problem.
32. Perhaps he is at home now. (用 could 表示可能性)
→ He ________ ________ at home now.
33. Is it possible that she knows the answer (用 can 提问)
→ ________ she ________ the answer
34. I’m sure that isn’t Sally. She’s in London. (用 can’t 表示否定推测)
→ That ________ ________ Sally. She’s in London.
35. Please help me carry this bag. (用 Could you... 提出请求)
→ ________ ________ ________ me carry this bag
36.They didn’t win the game. (用 couldn’t 表示过去的能力)
→ They ________ ________ the game.
37. It is possible that it will rain tomorrow. (用 can 表示可能性)
It ________ ________ tomorrow.
38. Do you have the ability to play chess (用 can 提问)
→ ________ you ________ chess
39. I want to know if it is possible to book tickets online. (用 Can I... 提问)
→ ________ ________ ________ tickets online
40. It’s impossible that he told a lie. (用 couldn’t 表示推测)
→ He ________ ________ ________ a lie.
IV. 完形填空（用 can, could, can’t, couldn’t 填空）
A: Hi, Mark. I called you last night, but you didn’t answer. Where were you
B: Oh, sorry. I (41) ________ hear the phone. I was at the cinema watching a movie.
A: A movie What was it about
B: It was a science fiction film. The characters (42) ________ travel through time!
A: That sounds cool. (43) ________ I borrow the DVD from you when you get it
B: Sure, you (44) ________. But I’m not sure when I’ll buy it.
A: That’s OK. By the way, (45) ________ you help me with my computer It (46) ________ start.
B: What’s wrong with it
A: I don’t know. It (47) ________ be a virus. I (48) ________ fix it myself.
B: Don’t worry. I (49) ________ come over tomorrow after school.
A: Really Thanks! You (50) ________ always solve computer problems.
B: No problem!
练习题答案与解析
I. 单项选择
1. B 【解析】表示过去的能力“我五岁时就会”，用could。
2. A 【解析】请求别人帮助，用Could you... 更礼貌。
3. A 【解析】表示理论上的可能性“山顶有时风会很大”，用can。
4. B 【解析】有把握的否定推测“那个人不可能是李先生”，用can’t。
5. A 【解析】请求许可用Could I... 更礼貌；给予许可用Yes, you can。
6. A 【解析】表示现在的能力“我哥哥现在弹得很好”，用can。
7. A 【解析】疑问句中表示推测“可能会是谁呢？”，用can。
8. A 【解析】表示现在的能力“我现在听不清”，用can’t。
9. C 【解析】提出建议，可以用You can... 或更委婉的You could...。
10. D 【解析】表示过去某种场合下“成功做到了”（赢得了比赛），用was able to。
11. B 【解析】疑问句推测用can；否定推测“不可能是老师”，用can’t。
12. A 【解析】请求对方做某事，询问“能力”，用Can you... 最直接自然。
13. D 【解析】请求许可用Can I... / Could I... / May I... 都可以；妈妈强调“必须”先完成作业，用must。
14. B 【解析】表示过去的能力“当时没能理解”，用couldn’t。
15. B 【解析】表示过去“没能来”的能力或可能性，用couldn’t。
16. C 【解析】有把握的否定推测“这个故事不可能是真的”，用can’t语气最强。
17. A 【解析】请求许可，May I... 是非常正式礼貌的说法。
18. B 【解析】表示过去的能力“上大学时能跑进4分钟”，用could。
19. B 【解析】征求意见“我该给你买什么？”，用What could I... 表委婉；回答“你可以买书”，用You can...。
20. B 【解析】表示过去的能力“当时没能听见”，用couldn’t。
II. 用 can, could, can’t, couldn’t, was able to 填空
21. can 【解析】现在的能力。
22. couldn’t 【解析】过去的能力/可能性“没能来”。
23. were able to 【解析】过去具体场合下“成功逃生”。
24. Could 【解析】询问过去的能力。
25. can’t 【解析】现在的能力“看不见”。
26. Can; can’t 【解析】询问现在的能力；否定回答。
27. could 【解析】过去的能力（她说她“能够”帮助我）。
28. can’t 【解析】有把握的否定推测“他不可能超过60岁”。
29. can 【解析】现在的能力“我们能听见”。
30. couldn’t 【解析】过去的能力“没能解决”。
III. 句型转换
31. could solve 【解析】表示过去的一般性能力，could 和 was able to 可互换。
32. could be 【解析】表示现在的可能性。
33. Can; know 【解析】询问可能性“她可能知道答案吗？”。
34. can’t be 【解析】有把握的否定推测。
35. Could you help 【解析】礼貌的请求。
36. couldn’t win 【解析】表示过去的能力“没能赢”。
37. can rain 【解析】表示理论上的可能性。
38. Can; play 【解析】询问能力。
39. Can I book 【解析】请求许可（询问可能性）。
40. couldn’t have told 【解析】对过去发生的动作进行否定推测“他不可能说了谎”。
IV. 完形填空
41. couldn’t 【解析】过去的能力“没能听见”。
42. could 【解析】电影里的能力“能够时空旅行”。
43. Can/Could 【解析】请求许可。
44. can 【解析】给予许可。
45. Can/Could 【解析】请求帮助。
46. can’t 【解析】现在的能力“无法启动”。
47. could 【解析】表示可能性“可能是个病毒”。
48. can’t 【解析】现在的能力“我自己修不了”。
49. can 【解析】现在的能力“我能过来”。
50. can 【解析】现在的能力“你总能解决”。
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