北木教育 > 托福 > 托福文章 > TOEFL实用语法系列——主语从句
发布时间:2018-09-18 北京智赢
从句指复合句中不能独立成句,但具有主语部分和谓语部分,由that、who、whom、when、why、where、how、which等引导词引导的非主句部分。
根据从句语法功能的不同,可分为:主语从句、表语从句、宾语从句、同位语从句、定语从句和状语从句六类。
前四类由于主语从句、表语从句、宾语从句及同位语从句在句子中的功用相当于名词,所以统称为名词性从句;
定语从句的功能相当于形容词,状语从句的功能相当于副词。
本期文章我们重点讲解的,就是主语从句:
在复合句中,充当主语成分的句子,例如"That he finished writing the composition in such a short timesurprised us all."——他在很短的时间内写完作文(这件事)让我们都很惊讶。描述的是“这件事”让我们惊讶,所以“这件事”是本句的主语,由此“That he finished writing the composition in such a short time”就是主语从句,充当整个复合句中的主语;“surprised”是主句的谓语;“us all”是主句的宾语。
引导主语从句的连词主要有:
从属连词:that whether
连接代词:who whoever whom whose what whatever which whichever
连接副词:when where how why
主语从句的用法及时态
1. 用法:
(1)连词位于句首不能省略,如:
That he finished writing the composition insuch a short time surprised us all.
(2)主语从句在绝大多数情况下视为第三人称单数,这时要注意主谓一致:
That they are the spies is impossible.
(3)有时为了防止句子头重脚轻,通常把形式主语it放在句首位置,真正的主语搁置于句末。
It is certain that he will win the match.
= That he will win the match is certain.
It is very likely that they will hold ameeting.
= That they will hold a meeting is verylikely.
2. 时态(所有名词性从句的时态都遵从以下规则):
(1)主句谓语动词是现在时(一般现在时、现在进行时、现在完成时等)或将来时(一般将来时、将来进行时),从句谓语动词可以用任何所需的时态。
Who will be our monitor hasn't been decidedyet.
Whom the watch belongs to is unknown.
(2)主句谓语动词是过去时(一般过去时、过去将来时等),从句谓语动词一般可用过去时(一般过去时、过去进行时、过去完成时、过去将来时)。
That they had waited for me half an hourwas very unlikely.
That she would go back home two weeks laterwas possible.
(3)客观的条件,从句时态不受影响。
That water freezes at thirty-two degreesFahrenheit was true.