情态动词的完成式:
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.
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