can't =cannot 的用法

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can't =cannot 的用法
can't =cannot 的用法

can't =cannot 的用法
英国人说can not 美国人说cannot
它们的缩写是can't
一、cannot …too… "不可能把某事做过头;决不会…太",与can never…too同义.
e.g.One cannot be too much careful."越小心越好."
二、cannot but + 动词原形,cannot help but + 动词原形,cannot help + 动名词,这三个短语在意义上基本相同,都表示"禁不住,不由得,不得不,不能不"的意思.cannot help + 动名词,是最规范的用法,最为常见.
e.g.I cannot help admiring the picture whenever I look at it."不管什么时候看到这幅画,我都禁不住要赞赏它."
"cannot but + 动词原形"主要用于美国英语,用法不大规范.
e.g.When the country calls you for help,you cannot but go."当国家需要你的时候,你不能不挺身而出."
"cannot help but + 动词原形",这种用法多见于非正式文体.
e.g.You cannot help but respect them."你禁不住会尊敬他们."
三、can but + 动词原形,cannot but + 动词原形意思不同,但又不能把后者简单地理解为前者的否定.can but + 动词原形 = can only.
e.g.I can but do my duty."我只能尽我的职责."
而cannot but + 动词原形 = must; to be forced to do something.
e.g.I cannot but go."我必须走."
四、"cannot have done","could not have done"都可以表示以现在的眼光看来,"过去还可能发生的事".
e.g.They cannot/ could not have gone out because the light is on!
但could not have done 还可以表示从过去某个时间点看来,"以前还可能发生的事.
e.g.The girl asked to see a timetable,feeling sure that her father could not have made such a mistake.
另外,cannot have done 要比could not have done 语气要强一些.
还有一点值得注意:could not have done 有其相对应的肯定形式,即could have done.而cannot have done 却没有其相对应的肯定形式,即是说can have done 只能用在否定句和疑问句中.
e.g.1) Where can he have gone?
2) She's two hours late -- What can have happened?
3) He can't have gone to Beijing --Just now I saw him.