虚拟语气和强调

虚拟语气

一般来说，表示以下三种情况时，动词常用虚拟语气：

1.与事实相反，不可能实现或难以实现的事

2.表示主观愿望，要求，建议，命令等

3.表示委婉语气主观推测

条件式虚拟语气

条件式虚拟语气一般用于表示与事实不符，不能实现或难以实现的事情。根据假设条件所涉及的时间，它可分成三类。

涉及现在条件句中1. be用were（也可用was）2. 其他动词用过去时主句中should，would，might，could+动词原形

涉及过去条件句中过去完成时had+过去分词主句中should，would，might，could+have+过去分词

涉及将来条件句中1.（should）+动词原形 2. were+动词不定式主句中用过去将来时（对于不易实现的事）；用一般将来时及一般现在时（对于能够实现的事）

If man made use of all the sunlight, he would have no need for coal or other fuels.

If the orbital motion of the earth were to cease, it would fall toward the sun.

The rule is not true if these restrictions be removed.

It would have taken them a long time to solve the complicated problem if electronic computers had not been used.

注意：

1.有些虚拟条件句的主句谓语动词与从句谓语动词的时态不一致，叫作“交错虚拟条件

句”。

What would happen if the boy on the bridge had thrown the stone?

2.if条件句中若有were，had，should，could等这类动词时，if可以省略，这时从句部分

应采用倒装语序。

Were the wire of a samm diameter, its resistance would be increased.

We would had arrived there on time had we caught the train.

Could a pin be drawn into a wire of the thickness of one atom, it would encirle the earth thousands of times.

3.虚拟语气中的条件从句，也可以由provided（that），in case，unless等引导；还可以由介

词without，under，but for，in the absence of等介词短语来表示条件；也可由副词（otherwise）引出条件状语。

Everything on the earth will lose its weight provided there be no gravity.

But for your help, we would not have solved the problem.

In the absence of gravity, there would be no air around the earth.

虚拟语气在名词性从句中的用法

名词性从句中的虚拟语气主要出现在主语从句，宾语从句，表语从句和同位语从句中，主要表示要求，建议，可能性，必要性，重要性，命令等。

名词性从句中的虚拟语气主要与主句中的某些形容词，及物动词和名词有关。

形容词：necessary，essential，important，imperative，possible，impossible，natural，desirable，等

及物动词：require，demand，suggest，desire，propose，order，recommend，request等

名词：requirement，suggestion，necessity，desire，recommendation，request，order，condition 等

其虚拟的形式均是：

从句引导词that+从句谓语“（should）+动词原形”+。。。

主语从句中

It is desirable that the resistance of the instrument be much smaller than that of the remainder of the circuit.

It is recommended that the reader use a pocket calculator to do the mathematical work required in basic electronics.

宾语从句中

The group suggested that the unit of length be based on the size of the earth.

They consider it important that proper attention be paid to the point.

表语从句中

Our suggestion is that this method be adopted.

同位语从句中

The requirement that energy be conserved must be fulfilled.

虚拟语气在状语从句中的用法

用在由as if，as though引导的从句中

如果涉及现在：be用were，其他动词用过去时。

如果涉及过去：谓语动词用过去完成时。

At that time the answer to the question seemed as if it had been wrong.

用在由whether。。。or。。。引导的让步状语从句中

这时，虚拟语气主要用在使用动词be的让步状语从句中。

All such problems, be they easy or difficult, can be solved by a computer.

用在由lest，in case，for fear that等表示的“以免”的从句中。

其谓语形式常用（should）+动词原形。

They (scientists) should be quick to respond to letters to the editor, lest animal rights misinformation go unchallenged and acquire a deceptive appearance of truth.

虚拟语气在主句和其他从句的用法

在这种情况下，虚拟语气主要表示主观推测或委婉语气。

should, would, could, might+动词原形

We might further ask how long it will be before the stone hits the water.

Planets that are very far from the sun are not places where living things could exist.

注意：

if only（但愿，要是。。。就好了），wish（愿望）, would rather(要是。。。就好了)后面跟的句子要用虚拟语气，其形式是：涉及现在或将来的动作或事情，谓语动词用过去时；涉及过去，谓语动词用过去完成时。在It is time（that）…的定语从句中，谓语要用一般过去时。

句子成分的强调