单个情态动词分析.doc

单个情态动词讲解
1. can (could) 
1).表示能力,意为“能,会”,用can, could, be able to均可,could是can的过去式。区别是:can只有过去时could,而be able to有多种时态。
John can speak three foreign languages fluently.
John could swim when he was four.
I regretted that I hadn’t been able to drive him home.
Will you be able to help me learn English tomorrow? 明天你能帮助我学习英语吗?
2)表示可能(理论上或是逻辑判断上)。
The temperature can fall to –60℃。气温可降至—60℃
Anybody can make mistakes.
表示推测或可能性,常用于否定句和疑问句
Can he be at school?
Today is Sunday. He can't be at school.
There is no light in the room. Can she have gone to bed?
对过去的推测
She could have gone out with some friends yesterday.
It was silly to throw the TV out of the window. It could have hit somebody.
You are late again. You could have got up earlier.
3)表示请求或许可( Could 比 Can 更加客气,can比may更正式)
Can I park my car in front of your office?
Can I have a look at your new pen? 
He asked whether he could take the book out of the reading—room. 
Could I use your bike now? ----Certainly. Go ahead. Yes, you can
4)表惊异、怀疑、不相信等态度。主要用于否定句、疑问句或感叹句中。
Where can (could) they have gone to? 他们会去哪儿了呢?
He can´t (couldn´t) be over sixty. 他不可能超过六十岁。
How can you be so careless? 你怎么这么粗心?
5)比较委婉客气地提出问题或陈述看法。
Can (Could) you lend me a hand? 帮我一把好吗?
I´m afraid we couldn´t give you an answer today. 恐怕我们今天不能给你答复。
2. may and might
1) 表示可能性; 表不太可能的推测, might可以指过去时间,也可以指现在时间,但语气更加不肯定, may/might have done 对过