一起过专四吧!(31)
文章作者 100test 发表时间 2007:06:26 11:24:29
来源 100Test.Com百考试题网
1. may和might 动词完成式
此结构用于推测过去的行为。例如:
She said that he might have missed the plane.她说他可能误了航班。
2. can和could 动词完成式
A. 表示过去能做而没做的事,有一种对过去未付诸实施的事情的惋惜。例如:
In those circumstances we could have done better.
在那样的情况下,我们本来可以做得更好的。(但没有做得更好)
B. 推测过去的某种行动。
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.
这孩子不可能那么快就把这本书读完的,因为即使对一个成人来说,这本书也是相当难的。
Note:
can t和couldn t+ 动词原形可以用来表示否定推断。例如:
He can t be over fifty.他不可能超过50岁。
3.must 动词完成式
表示对过去行为的推断,具有较大的可能性,意为“一定…,想必…”。例如:
She must have gone through a lot.
她一定吃过很多苦。
Note:
must+动词原形→对现在的推测,must be+现在分词→对未来或现在正在进行的推测。例如:
She looks happy. she must be having a good time.
4. needn t+动词完成式和didn t need to do
A. needn t+动词完成式表示一种已经做过的但并无必要的行为。例如:
You needn t have watered the flowers, for it is going to rain.
你本来不必浇花的,因为天要下雨了。(但却浇了)
We needn t have told him the news because he knew it already.
B. didn t need (have) to do结构表示没有必要做某事,实际上也没有做。例如:
I didn t need to clean the windows. My sister did it.
我不必擦窗,我妹妹擦了。(我没有擦)
5. should 动词完成式
A.此结构的肯定式表示应该做的事而没有做,否定式表示某种行为不该发生但却发生了。例如:
You should have given her more help.
你应该多给她一些帮助的。(但没有给)
B. 表示推测,意为“可能”,但可能性较小。例如:
He should have finished the work by now.
他现在该把工作完成了。(推测)
C. should / would have thought意为“本以为,本认为”。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.
我本来认为她不会同意的。
D. should have thought有时意为“认为,以为”,相当于should think,但表示更为委婉、谦逊或不肯定的语气。例如:
I should have thought it fairly good.
我以为它是很不错的。
E. should have + 过去分词用于虚拟语气:
Had you written him, you should have known the details.
6. ought to 动词完成式
此结构表示某种过去应该做而没有做的事,或被忽略未做的某种明智行为。例如:
You ought to have returned the book earlier.(还晚了)
You ought to have refused her at the beginning, but now it is too late.
Note:
这里的ought to也可以用should代替。