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O-Level语法：复合句的时态归纳总结

在新加坡，O水准考试的成绩不仅仅会决定你进入哪所学校学习，还会在一定程度上影响你今后的就业情况。如果学生想要申请出国留学的话，那么O水准考试更是不能掉以轻心。下面小编就和大家一起看看语法复合句中，主句和从句的时态关系如下：

定语从句：定语从句的谓语和主句谓语之间没有必然关系；

宾语从句：宾语从句受主句影响，如果主句是现在时，从句可以用任何时态；如果主句是过去时，从句谓语一定要用过去的时态（一般过去时、过去进行时、过去将来时、过去完成时）；如果从句是客观事实，从句谓语必须用现在时；

状语从句：主句和从句之间的时态一致问题一般分为下列几种情况：

1.主情从现：主句中有情态动词时，从句用一般现在时表示将来。如：

①The traffic must stop when the lights turn red.

2.主祈从现：主句是祈使句时，从句用一般现在时表示将来。如：

①Be careful when you cross the road.

3.主将从现：主句用一般将来时，从句用一般现在时表示将来。如：

①I will visit my good friend when I have time.

②If she comes here tomorrow, I will go to the park with her.

3.Before: It will be +时间段+ before +一般现在时; it was +时间段+ before +一般过去时；Before引导的时间状语是过去时，主句可以用一般过去时或过去完成时

4.宾语从句和状语从句同时出现。如：

①I don't know if he will come. If he comes, I will tell him about the accident.

②I don't know when he will come tomorrow. When he comes, I will tell him about the accident.

5.as when while的区别和用法

1.当从句中的谓语动词是持续性的动作，主句是短暂性动词可以用while,when或as。eg：While / When / As I was walking down the street, I noticed a police car in front of the bank.2.当从句中的谓语动词表示瞬间动作时,不可用while。eg:He was on the point of leaving when someone knocked at the door.3.如果谈论两个长动作,最常用的是while。eg：While John was biting his nails, I was working out a plan to get us home.

注意：

1、若主句与从句表示的是两个同时发生的短暂性动作，含有类似汉语“一……就”“刚要---就”的意思，英语一般要用as (也可用when)。如：

The ice cracked as [when] I stepped onto it.我一踩冰就裂了。

He is about to go out when it rains.他刚要出门就下起了雨

2.若要表示主句动作伴随从句动作同时发展变化，有类似汉语“随着”的意思，英语习惯上要用as，而不用when或while。如：

The room grew colder as the fire burnt down.

As time goes by my memory seems to get worse.

注：若不是引导从句，而是引出一个短语，则用with，不用as。如：

With winter coming on, it’s time to buy warm clothes.

3.若暗示一种规律性，表示“每当……的时候”，英语一般要用when。如：

It’s cold when it snows.

He smiles when you praise him.