江苏省明德实验学校2012-2013学年高一下学期英语M4Unit 2 Grammar
1. 一年前我不会开车，但是现在我会了。 I couldn't drive a year ago, but now I can. 2. 作为一个公民，你应该遵守法律。 As a citizen, you should obey the law.
can could may might shall should will would must need dare ought to
情态动词 + 动词原形
1 can could 1)表能力 （可以用be able to 代替） I don’t think he can solve the problem without any help. I couldn't drive a year ago, but now I can.
can 只有一般式和过去式could, 而 be able to 有原形be able to，有现在时态的am/is/are able to， 过去时态was/were able to， 有将来时态 will/would be able to，完成时态 has/have been able to等
be able to 除了可以与can互用表示能力以外，还可以指经过努力而 成功地办到了某个具体的事情，相当于manage to或者succeed in, 不可以用can。 My brother can play table tennis. He was able to flee from the prison.
Despite his enormous workload the President still seems able to
find time to go fishing. I haven't been able to read that report yet. She couldn't climb the mountain.(没有能力爬，因此也没爬) She was not able to climb the moutain.(尝试爬过，但没能爬上去)
2) 表示许可或者请求许可（正式场合用may） Can you help me to work out this maths problem? You can borrow two books at a time from the library. 3）表示可能性，用于推测，常用于疑问句和否定句中,指“某事是否是事实”（肯定句 中要用may) Can it be true?----It can be true. Can he be so selfish? Can he be living there? Can the hall seat a thousand people?