专升本英语语法——虚拟语气

虚拟语气是动词的特殊形式，用来表达说话人的意愿、建议、请求、意图、惊奇、设想等未能或不可能成为事实的情况，以及在说话人看来实现的可能性很小的情况。

虚拟语气是非常重要的语法考点。考查历届试题，我们发现与虚拟语气有关的考题每次至少2题，有时甚至3-4题。虚拟语气的考查要点有：

1. 虚拟语气的形式：

分清虚拟时间和主从句的动词形式十分重要。

2. 要注意从句中第一/三人称的过去式was用were代替。

例如：

If I were invited, I would come.

If she were not ill, she could do a lot of things.

3. if条件句中如谓语动词是were, had, should, could时，可以省略if, 把它们前置。

例如：

Had my father a lot of money, he would send me abroad.

Could I do it, I would surely do it.

Should the Black Death reappear, what should we do?

(万一黑死病再次出现，我们该怎么办?)

4. 错综时间的条件句是难点

If I hadn’t stood under the ladder to catch you when you fell, you wouldn’t be smiling now.(从句用过去完成时，主句用现在进行时)

又如：

If I were you, I would have gone to the film last night.

(从句虚拟现在，主句虚拟过去);

If we hadn’t got everything ready by now, we should be having a terrible time tomorrow.(从句虚拟过去，主句虚拟将来);

If the weather had been more favorable, the crops would be growing still better.(从句虚拟过去，主句虚拟现在)

5. 虚拟句的另一难点是省略if条件句的含蓄条件句，

如：

I would have written the paper before, but I have been ill.

(=If I had not been ill, I would have written the paper before.);

A true friend would have acted differently.

(=A friend, if he had been true, would have acted differently.)

6. 注意介词短语 without, but for, in the absence等表示虚拟条件。

例如：

Without electricity, there would be no modern industry.

没有电就不会有现代工业。

But for your cooperation, we could not have succeeded in our experiment.没有你们的帮助，我们的实验是不可能成功的。

7.“Were it not for/Had it not been for+宾语”或“But that+从句”表示假设条件。

例如：

Were it not for their assistance, we couldn’t have got over the difficulties.

Had it not been for the reservoir, we’d never have been able to beat the drought.

But that he saw it (=If he had not seen it), he could not have believed it.

8.providing, providing (that), on condition that, suppose, supposing引导的条件从句中，根据语意，可以用虚拟语气，有可以用陈述语气。

9.常见的引导宾语从句须用虚拟语气的动词有：

advice, agree, command, decide, demand, determine, direct(命令)insist, order, prefer, propose, request, require, resolve, suggest, urge, move(提议，动议)等;

例如：

The United Nations urged that he (should) withdraw his troops.

(联合国敦促他撤军。)

10.常见的引导同位语从句或表语从句须用虚拟语气的名词有：advice, command, desire, determination, idea, motion, order, preference, recommendation, suggestion, insistence, proposals, request, requirement等;

例如：

The suggestion that he be invited was rejected. (用于同位语从句)

邀请他的建议被否决了。

Their demand is that their wages be increased by 20%. (用于表语从句)

他们的要求是工资增加20%。

11.用在主语从句中时其结构通常为“It is/was + 形容词或过去分词+主语从句(用虚拟语气)”，

例如：

It is necessary that you should be present at the discussion.

你有必要参加讨论。

It was ordered that the medicines be sent here by plane.

根据命令，那些药品必须空运到这儿。

常见的这类形容词、分词还有：advisable(合理的), anxious(急切的), appropriate(合适的), compulsory(强制的), crucial(紧要关头的)，desirable(理想的), eager, essential(必要的), imperative(迫切的), important(重要的), impossible(不可能的), improper(不合适的), natural(自然的), obligatory(必须履行的)， preferable(更好的), proper(合适的), strange(奇怪的)urgent(紧迫的), vital(至关重要的), demanded(要求的), required(要求的), suggested(建议的), desired(希望的)等。