专四必备语法:情态动词

发表时间:2015-11-23内容来源:VOA英语学习网

七、情态动词

注意情态动词完成式的用法有两方面的含义:

1.表示已经发生的情况

(1)must have +过去分词,表示对已发生情况的肯定推测,译为“(昨天)一定……”。如:

My pain must have been apparent the moment I walked into the room, for the first man I met asked sympathetically: “Are you feeling all right?”

(2)can’t/couldn’t have +过去分词,表示对已发生情况的否定推测,译为“(昨天)一定没……”。 如:

Mary couldn’t have received my letter; otherwise she would have replied before now.

(3)may/might have +过去分词,表示对已发生的事情做不肯定、可能性很小的推测,或事实上根本没发生,译为“也许……”。如:At Florida Power’s Crystal River plant, a potentially serious leakage of radioactive water may have been unknowingly caused by an electrician.

2.表示虚拟语气

(1)needn’t have+过去分词,表示做了不必做的事,译为“其实没必要……”。如:

As it turned out to be a small house party, we needn’t have dressed up so formally.

(2)should /should not have +过去分词,表示应该做某事但实际上未做,或本不应该做但实际上做了, 译为“本(不)应该……”。如:I regret having left the work unfinished; I should have planned everything ahead carefully.

(3)ought to have+过去分词,表示动作按理该发生了,但实际上未发生,译为“该……”,与should的完成式含义类似。如:

The porter ought to have called the fire-brigade as soon as he saw the fire in the stock, which went up in smoke.

(4)could have+过去分词,表示过去本来可以做但却未做,译为“完全可以……”。如:

What you said is right, but you could have phrased it more tactfully.

(5)may/might have + 过去分词,表示过去可以做但实际未做,译为“(那样)也许会……”。如:

It might have been better to include more punchy statistics and photos of equipment in the introduction to further assist first-time office automation managers.

3.几个情态动词常考的句型

(1)may/might (just) as well“不妨,最好”,与had better相近。如:

Since the flight was cancelled, you might as well go by train.

(2)cannot/can’t…too… “越……越好,怎么也不过分”。注意这个句型的变体cannot…over…。如:

You cannot be too careful when you drive a car.

The final chapter covers organizational change and development. This subject cannot be overemphasized.

(3)usedn’t或didn’t use to为used to (do)的否定式。

(4)should 除了“应该”一层意思外,大纲还规定要掌握其“竟然”的意思。如:

I didn’t expect that he should have behaved like that.

 

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