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if状语从句与虚拟语气

2017-04-14徐志清

高中生学习·高三版 2017年4期
关键词:虚拟语气原形主句

徐志清

if引导的状语从句是英语高考中的高频考点,同学们很容易在这个考点上犯错。特别是学习了虚拟语气以后,看到if从句就容易把它当成虚拟条件句,导致从句谓语动词选用虚拟形式。这说明这些同学还没有完全理解if引导的状语从句。为了让同学们更好地掌握if引导的状语从句,笔者针对if引导的从句作了如下小结。

[if引导的条件状语从句]

if条件句根据表达的内容可分为真实条件句和虚拟条件句,也就是说if引导的虚拟语气只是条件句的一种。

1. 真实条件句

凡是假设的情况发生的可能性很大,就是真实条件句。如:

If I have time, I will help you with this work.

If time permits, well go fishing together.

2. 虚拟条件句

当假设的情况不大可能实现时,就用虚拟条件句。如:

If I were you, I would have attended the meeting。

If he had come here yesterday, he would have seen his old friend。

3. 对虚拟语气的判断

判断是真实条件句还是非真实条件句,主要是通过句子意思,看假设的条件是否能够实现。假设的条件能够实现是真实条件句,假设的条件不能实现则是虚拟条件句,要用虚拟语气。最基本的虚拟语气句型有以下三种。

(1)虚拟语气的现在时表示与现在事实相反的假设,从句的谓语形式用动词的过去式(be动词一般用were),主句用“would/should/could/might+动词原形”。

If I were you, I wouldnt go there.

(2)虚拟语气的过去时表示与过去事实相反的假设,if从句的谓语用过去完成时,即“had+过去分词”,主句用“would/should/could/might+have+过去分词”。如:

If he had known your address yesterday, he would have telephoned you.

(3)虚拟语气的将来时表示对将来实现的可能性很小的或不确定的假设。从句的谓语用一般过去式或用“were to/should+动词原形”,主句用“would/should/could/might+動词原形”。如:

If he were to leave today, he would get there by Friday。

注意在if引导的真实条件句中,从句常用一般现在时表示将来时,主句用一般将来时。

在if引导的虚拟条件句中,注意主句和从句中的动词要按虚拟语气的形式(分现在、过去、将来三种类型)搭配恰当,不能随意。在if引导的虚拟条件句中,如果主句和从句所表达的时间不一致,这种句子叫混合型虚拟语气,主句和从句分别按各自的时间选择时态。如:

If you had finished the work yesterday, you would play with us now.

[only if和if only引导的从句]

在if only(如果……就好了)引导的感叹句中,谓语动词用虚拟语气形式,分为三种情况。

1. 表示与现在事实相反的假设,从句的谓语形式用动词的过去式(be动词一般用were)。

2. 表示与过去事实相反的假设,从句的谓语形式用过去完成时即“had+过去分词”。

3. 表示与将来事实相反的假设,从句的谓语形式用“would/could/might+动词原形”。

If only he didnt drive so fast! (对现在的虚拟)

If only she had asked someones advice. (对过去的虚拟)

If only the rain would stop. (对将来的虚拟)

而only if引导的从句放在句首时,其主句要部分倒装。如:

Only if he gives you enough money, can you buy a new coat.

Only if he is here, can the problem be solve.

[as if引导的状语从句]

在as if/as though从句中,也分为真实条件句和虚拟条件句。

1. 表达不可能发生的事情,用虚拟语气。

如果表示与现在事实相反,从句谓语动词用过去式(be的过去式用were);如果表示与过去事实相反,从句谓语动词用过去完成式(had+过去分词);如果表示与将来会发生的事实相反,从句谓语动词用“would/could/should+动词原形”。如:

He speaks as if he were on the spot.

This device operated as though it had been repaired.

He opens mouth as if he would say something.

2. 如果有可能成为事实, 用陈述语气。如:

He looks as if he is going to be ill.

[even if引导的状语从句]

Even if/even though引导的让步状语从句如果表示真实的条件,就用陈述语气。如:

He wont come here even if he is invited.

但是even if也可以表示一种不可能的事实,就用虚拟语气。如:

Even if he were here, he couldnt solve the problem.

Even if you hadnt read the book, you could have written the article.

Even if he were to go to America next week, he would come to attend your party.

[what if引导的状语从句]

“what if+陈述句”构成问句,意为“如果……会怎么样”。这种句型常用一般现在时表示将来。如:

What if it rains tomorrow?

What if he cant finish it?

以上几种常用句型都是同学们经常遇到的,同学们只有反复练习,仔细分析它们中的每一句所表达的内容是否能够实现,才能准确判定它们的形式,更好地运用这些句型。

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