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2017年專業(yè)英語四級考試詞匯語法輔導(dǎo)1

時間:2017-03-02 16:36:00   來源:中大網(wǎng)校     [字體: ]
學(xué)習(xí)情態(tài)動詞+完成時的用法.

1. may和might+ 動詞完成式

此結(jié)構(gòu)用于推測過去的行為。例如:

She said that he might have missed the plane.她說他可能誤了航班。

2. can和could+ 動詞完成式

A. 表示過去能做而沒做的事,有一種對過去未付諸實(shí)施的事情的惋惜。例如:

In those circumstances we could have done better.

在那樣的情況下,我們本來可以做得更好的。(但沒有做得更好)

B. 推測過去的某種行動。

Where can /could she have gone? 她可能到哪里去了呢?

The boy can’t have finished reading the book so soon because it is difficult even to an adult.

這孩子不可能那么快就把這本書讀完的,因?yàn)榧词箤σ粋成人來說,這本書也是相當(dāng)難的。

Note:

can’t和couldn’t+ 動詞原形可以用來表示否定推斷。例如:

He can’t be over fifty.他不可能超過50歲。

3.must +動詞完成式

表示對過去行為的推斷,具有較大的可能性,意為“一定…,想必…”。例如:

She must have gone through a lot.

她一定吃過很多苦。

Note:

must+動詞原形→對現(xiàn)在的推測,must be+現(xiàn)在分詞→對未來或現(xiàn)在正在進(jìn)行的推測。例如:

She looks happy; she must be having a good time.

4. needn’t+動詞完成式和didn’t need to do

A. needn’t+動詞完成式表示一種已經(jīng)做過的但并無必要的行為。例如:

You needn’t have watered the flowers, for it is going to rain.

你本來不必澆花的,因?yàn)樘煲掠炅恕?但卻澆了)

We needn’t have told him the news because he knew it already.

B. didn’t need (have) to do結(jié)構(gòu)表示沒有必要做某事,實(shí)際上也沒有做。例如:

I didn’t need to clean the windows. My sister did it.

我不必擦窗,我妹妹擦了。(我沒有擦)

5. should +動詞完成式

A.此結(jié)構(gòu)的肯定式表示應(yīng)該做的事而沒有做,否定式表示某種行為不該發(fā)生但卻發(fā)生了。例如:

You should have given her more help.

你應(yīng)該多給她一些幫助的。(但沒有給)

B. 表示推測,意為“可能”,但可能性較小。例如:

He should have finished the work by now.

他現(xiàn)在該把工作完成了。(推測)

C. should / would have thought意為“本以為,本認(rèn)為”。例如:

A: "Can you type?"

B: "Certainly."

A: "Well, I should have thought you wouldn’t."

I should have thought she wouldn’t agree.

我本來認(rèn)為她不會同意的。

D. should have thought有時意為“認(rèn)為,以為”,相當(dāng)于should think,但表示更為委婉、謙遜或不肯定的語氣。例如:

I should have thought it fairly good.

我以為它是很不錯的。

E. should have + 過去分詞用于虛擬語氣:

Had you written him, you should have known the details.

6. ought to + 動詞完成式

此結(jié)構(gòu)表示某種過去應(yīng)該做而沒有做的事,或被忽略未做的某種明智行為。例如:

You ought to have returned the book earlier.(還晚了)

You ought to have refused her at the beginning, but now it is too late.

Note:

這里的ought to也可以用should代替。

Homework:用給出的動詞填空,注意要選用正確的助動詞和時態(tài).

1.The boy____ the book so soon because it is difficult even to an adult. (read)

2.We___him the news because he knew it already. (tell)

3.If we had taken the other road, we ____earlier. (arrive)

4.I _____you might take this into consideration. (think)

5.You ____ her at the beginning, but now it is too late.(refuse)