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.
将常用、常考的几个情态动词完成式列表说明如下:
It must have rained last night; the ground is wet.(昨晚准是下雨了,地上湿漉漉的。)
The baby was cut badly; she shouldnt (oughtnt to) have let him play with the scissors. (孩子伤得很厉害;她不该让他玩剪刀。)
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