go home in this weather.
f. 表示惊异，怀疑不相信的态度．(主要用在否定句、疑问句或惊叹句中)如： Can this be true?
How can you be so rude! This cannot be done by Mary.How can you be so rude! 注意：can 与be able to 区别：
can表能力，只用一般过去时和一般现在时
be able to表能力+成功，即
最终设法做成了某事。有各种时态,可以与别的情态动词连用。
The fire spread through the hotel very quickly, but everyone ______ get out.（NMET97）
A. was able to B. could C. had to D. would g. 固定句型
can not … too /can never … too 再也不过分
You can never be too careful.
We can never attach too much importance to balanced diet.
2. may / might
a. 表示允许, might 语气更委婉
在表示请求、允许时，mig比may的语气更委婉一些，否定回答时要用mustn't，表示
\不 可以\、\禁止\、\阻止
之意．如：
You may drive the car． --Might l use your pen? --No，you mustn't . 用May I．．．征询对方许可在文体上比较正式，在口气上
比较客气。在日常口语中，用Can I．．．征询对方意见更 为常见。
May I use your ruler? --- Yes, help yourself. / Yes, you may.
--- No, you mustn’t.