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高考英语语法精要讲解二十六:情态动词

发布时间:2016-02-29  编辑:查字典英语网小编

  高考英语语法精要讲解二十六:情态动词

    1、情态动词 + have done sth

    这个结构有着特殊意义:用来表示猜测(设想可能发生过什么事情)或

    想象(设想可能出现过什么不同的情况)

    ①should (ought to) have done sth 本来该做而未做

    This wall oughtnt to have been painted blue.

    ②need have done sth 本来有必要做而未做

    You neednt have told her the news.

    ③must have done sth 对过去所做动作的肯定推测

    ---We went to Paris.

    ---That must have been nice.

    ④can have done sth 对过去所做动作的否定或疑问推测

    I dont think he can have heard you. Call again.

    Where can John have put the matches?

    ⑤may (might) have done sth 过去可能发生某事,与could相比,may和 might可能性较小,might 可能性更小;might 也可表示过去可能发生而未发生的事情。

    Pollys very late----she may (might) have missed her etrain.

    You were stupid to try climbing there. You might have killed youself

    ⑥could have done sth

    ●推测过去可能发生某事 (同can, 但can不用肯定句)

    She could have gone off with some friends.

    ●表示过去没有实现的可能性:某事可能发生,但却没有发生

    You were stupid to go skiing there----you could have broken your leg.

    ●表示有能力做而未做(虚拟语气)

    You could have helped me !

    (You were able to help me, but you didnt.)

    2、can could be able to 表示能力

    ●can 通常表示现在的或一般的能力---即你无论什么时候想做就能

    做到的能力, 指单纯的表示一个人有某种能力。

    You can certainly cook, even if you cant do anything else.

    ●be able to表示某人通过努力、克服困难做成某事。

    will be able to 表示将来的能力

    Ill be able to speak German in another few months.

    ●could 表达 一般的能力---即你过去想干什么就可以干什么

    She could sing like an angel when she was a kid.

    但could 不能表达过去某种具体的能力,此时用was able to, managed to 或 succeeded in 等

    How many eggs were you able to get ?

    3、can, could, may和might 表示可能性

    ●可用来表示:①理论上的可能性(不涉及是否真发生);②提出建议

    (提出解决某个问题的可能办法或者采取的行动);③在问句或否定句中表达现在的可能性)

    Anybody who wants to can become a prison visitor.

    ①---What shall we do ?

    ---We can try asking Lucy for help. ②

    Who can that be at the door ? Can it be Polly?    ③

    ●may 可用来表达:①将来的可能性;②说话时某事可能是真实的

    We may go climbing this summer.   ①

    You may be right.          ②

    ●could / might 可用来表示: ①说话时某事可能是真实的;②将来

    某事有可能发生,但不表示特别可能发生。

    You could be right, but I dont think you are.  ① 

    It could rain later on this evening.     ②

    4、can, could, may 和might表示允许

    ①请求允许:它们都可以表示请求允许做某事,could 和 might并不是表示过去

    Can (May, Could) I borrow your umbrella ?

    ②允许:当我们允许某人做某事时,我们用can和may来表达,而不能使用could和might

    You may / can watch TV for as long as you like. (不用could, might; mustnt 有拒绝的意思)

    ---Could I use your phone?

    ---Yes, of course you can /may. (No, you cant / may not.)

  

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