情态动词can 的用法小结
情态动词是高考的考点，对中学生来说也是个难点，而can的用法较其他情态动词多，现根据中学课本和近几年的高考试题，将其重点内容列出。
一．表示能力
1．Can you type?
2．I can do it.
can 与be able to 的区别
1. be able to 能用于各种时态。“设法做成某事” 相当于 managed to do sth.. / succeeded in doing sth.。
2. can / could 只能表示现在或过去的能力。
例：
1） A computer ______ think for itself; it must be told what to do.
A. can’t B. couldn’t
C. may not D. might not
析：答案是A，表示能力.
2）. The fire spread through the hotel very quickly , but everyone ______ get out.
A. had to B. would
C. could D. was able to
析：答案是D。表示经过努力才成功地逃出大火。
二．can/could 表示许可/允诺
1．Can/could Tom use the car?
Yes , he can.
与may /might 的区别
1．might, could 比较委婉, 一般多用于疑问句.
2．在以could, might 表示征询对方意见或表示请求时，回答应相应使用can, may.
例：
1）. — Could I borrow your dictionary?
— Yes, of course you _______.
A. might B. will C. can D. should
析：答案是C。第一句的请求用could，所以回答时相应用can
2.） — Might I watch TV after supper?
— Yes, you ________.
A. may B. must C. might D. can
析：答案是A。第一句的请求用might，所以回答时相应用may.
3）.---Could I call you by your first name?
---Yes, you _____.
A. will B. could
C. may D. might
析：答案是C。第一句的请求用could，回答时相应用can, 但选项中没有can，所以最佳的是may.
三．can指可能性
He can’t be at home. He has gone to Beijing.
与must may , might, could /Should, ought to的区别
1.should, ought to:按理应当, 很可能
2.must：表示肯定的猜测
3.may /might：表示可能的猜测
4.can/could：表示否定或疑问的猜测
例：
1） -when can I come for the photo ? I need them tomorrow.
-- They ____ be ready by 12:00
A. can B .should C. might D. need
析：答案是B。根据情景，应表示可能的猜测，选might可能会走掉顾客
2）Peter ___ come with us tonight, but he isn’t very sure yet.
A. must B. may
C. can D. will
析：答案是B。根据he isn’t very sure，表示可能的猜测
3）.Michael ___ be a policeman, for he is much too short.
A. needn’t B. can’t C. should D. may
析：答案是B. 根据for he is much too short，可以判断是表示否定的猜测
4）----_____he be watching TV now?
— Yes, he _____ be watching TV now.
— No, he _____ be watching TV now.
A. Must; can; mustn’t B. Ca
n; must; can’t
C. Can; can; mustn’t D. May; must; needn’t
析：答案是B。第一句和第三句分别表示疑问和否定的猜测，第二句表示肯定的猜测。
四. can /could have done
1 过去有能力做到而实际上没有做到的事情.含有责备或劝告之意。
2 用于否定句,对过去发生事情的否定猜测.
例：
1）. ---There were already five people in the car, but they managed to take me as well.
----It ____a comfortable journey
A. can’t be B. shouldn’t be
C. mustn’t have been D. couldn’t have been
析： 答案是D。根据上下文，已经有5个人在车上，但还是把我带上，所以，这次路途不可能是舒服的，属于否定的猜测。而第一句的时态用过去时，所以是对过去发生事情的否定猜测.
2） You made a lot of mistakes in your composition yesterday. You ________ it much better.
A. can write B. could have written
C. must have written D. should write
析：答案是B。意为：昨天你在作文里犯了很多错误，你本应有能力把它写得更好，含有责备的语气。