职称英语《综合类》考试语法讲解:情态动词-查字典英语网
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职称英语《综合类》考试语法讲解:情态动词

发布时间:2016-03-02  编辑:查字典英语网小编

  can / may / should / ought to / must / need等动词称为情态动词。情态动词有三大特征:一是无人称和数的变化,二是后面跟的动词不带to,三是后面 + not构成否定式,比较:

  He neednt go there so early.

  You do not need to be an expert to make this simple design.

  在讲解情态动词完成式前,先将一般式中应注意的几个问题提一下,以引起必要的重视。

  1.情态动词一般式中应注意的几个问题:

  注意以下用法的习惯与区别:

  He must be a doctor.

  否定:He cant be a doctor.

  又如:They cant be working now.

  May I go now?

  回答:Yes, please. / Please dont.

  have to 与 must

  1) 当强调外界原因时,2) 当与将来时结合时,用have to,

  例如:

  Since it is raining, we have to sty indoors.

  You will have to hurry if you want to catch the 9:30 train.

  3) 表示自然规律或必然结果,用must,

  例如:

  All men must die.

  can 与be able to

  can表示能力,但不一定做了或做成了;be able to 表示有能力并且做成了,相当于succeed in doing, 例如:

  The patient is able to walk now.

  The patient can walk now.

  Shall I / we? 表示征求对方意见; + shall表示允诺或警告,例如:

  Shall I fetch a doctor for you?

  You shall be sorry for what you have done.

  Will you.? 表示请求, 例如:

  Don be late for the meeting next time, will you?

  比较:I would remind you that smoking is forbidden here.

  neednt 的肯定式为must,例如:

  You neednt see him, but I must.

  cannot but + 原形动词 , 例如:

  I cannot but tell you the truth.

  2.情态动词的完成式:

  情态动词的一般式用于表达现在或将来的情况,而情态动词的完成式则用来表达已经发生的事情,例如:你不应该来得那么晚。这是对已经发生的事情表示自己的看法:You shouldnt have come so late.

  

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