高中英语知识点:主语从句
◎ 主语从句的定义

主语从句的概念:

如果一个句子在复合句中充当一个主语,那么这个句子就是主语从句。主语从句通常由从属连词that,whether,if和连接代词what,who,whichwhatever,whoever以及连接副词how,when,where,why等词引导。that在句中无词义,只起连接作用。

◎ 主语从句的知识扩展
1、that引导的主语从句
   That只起连接作用,无词义,在从句中布作成分,一般不能省略。
   That he will come and help us is certain.
2、whether/if引导的主语从句
   Whether引导的主语从句既可放在句尾,但if引导的主语从句只能放在句尾,前面用it作形式
   Whether/if 只起连接作用,译成“是否”,在从句中布作成分。
   Whethe it is ture remains a question.
   It is doubtful whether the manager knew the datails of the plan.
3、wh-类连接词引导的主语从句
   Wh-类连接词除起连接作用外,还在从句中作成分。连接代词主要作主语、宾语、表语、定语等;
   连接副词在从句中作状语。
   What you are doing is very difficult. (作宾语)
   Whoever breaks the law should be punished. (作主语)
   Who will do the job has not been decided. (作主语)
   When we shall have our sports meet is still a question. (作状语)
4、It+谓语+主语从句
   有时主语从句放在句首,句子显得笨重,常把主语从句移到句末,用it作形式主语。常用句型有
   以下四种:
1)It+系动词+形容词+that/wh-从句
   It is likely that there will be a snowstorm tomorrow.
2)It+系动词+名词+that/wh-从句
   It is a pity that you didn’t attend the lecture yesterday.
3)It+系动词+过去分词+that/wh-从句
   It is known to all that the earth is round.
4)It+不及物动词+that/wh-从句
   It seems to me that you object to the plan.
5、主语从句应注意的几个问题
1)that引导的主语从句既可放在句首,也可放在句尾,但在下列情况下that从句不可提前。
  (1)在It is said/reported…that结构中。
       It is reported that a bank was robbed yesterday.
  (2)在It happened/occurred…结构中。
       It happened that the teacher was not in the office that day.
  (3)含主语从句的复合句是疑问句时。
       Is it ture that you will give up the job?
2)下面这种情况常用it作形式主语。
   在It doesn’t matter+what/whatever…结构中。
   It doesn’t matter what you say.
3)由what引导的主语从句谓语动词单复数问题
   what引导的主语从句一般按单数对待,但是,在实际使用中究竟按单数还是按复数对取决于
   其成分的含义。
   What we need is more time.
   What were left behind were five empty bottles.
◎ 主语从句的知识点拨

主语从句用法:

1、主语从句的引导词:
主语从句通常由连词that和whether、连接代词或连接副词以及关系代词型what引导:
如:That he is still alive is a wonder. 他还活着,真是奇迹。
        When we arrive doesn't matter. 什么时候到没有关系。
        What we need is money. 我们需要的是钱。
        What I want to know is this. 我想知道的就是这一点。
        Whether they would support us was a problem. 他们是否会支持我们还是一个问题。

2、主语从句与形式主语it:
有时为了考虑句子平衡,通常在主语从句处使用形式主语it,而将真正的主语从句移至句末。这分三种情况:
(1)对于以连词that引导的主语从句,通常用形式主语代主语从句:
如:It's a pity that he didn't come. 很遗憾他没来。
(2)对于以连接代词(副词)引导的主语从句,可以使用形式主语代主语从句,也可直接在句首使用主语从句:
如:Whether they would support us was a problem. 他们是否会支持我们还是一个问题。  
        It was a problem whether they would support us. 他们是否会支持我们还是一个问题。
(3)对关系代词型what引导的主语从句,通常不用形式主语,总是主语从句放在句首:
如:What we need is money. 我们需要的是钱。
        What I want to know is this. 我想知道的就是这一点。
(4)如果句子是疑问句,则必须用带形式主语it的结构:
如:Is it true that he is the girl's father? 他是那女孩的父亲,是真的吗?
        How is it that you are late again? 你怎么又迟到了?

3、连词that的省略问题:
引导主语从句的连词that有时可省,有时不能省,其原则是:
若that引导的主语从句直接位于句首,则that不能省略;
若that引导的主语从句位于句末,而在句首使用了形式主语it,则that则可以省略:
如:That you didn't go to the talk was a pity. 很遗憾你没去听报告。(that不可省)
        It was a pity(that) you didn't go to the talk. 很遗憾你没去听报告。(that可省)

◎ 主语从句的知识拓展

主语从句应注意的几个问题:

1、that引导的主语从句既可放在句首,也可放在句尾,但在下列情况下that从句不可提前。
(1)在It is said/reported...that结构中:
如:It is reported that a bank was robbed yesterday.
(2)在Ithappened/occurred...结构中:
Ithappenedthattheteacherwasnotintheofficethatday.
(3)含主语从句的复合句是疑问句时:
如:Is it ture that you will give up the job?
2、下面这种情况常用it作形式主语。在It doesn't matter+what/whatever…结构中。
如:It doesn't matter what you say.
3、由what引导的主语从句谓语动词单复数问题 what引导的主语从句一般按单数对待,但是,在实际使用中究竟按单数还是按复数对取决于其成分的含义。
如:What we need is more time.
        What were left behind were five empty bottles.

◎ 主语从句的教学目标
1.理解并掌握主语从句的概念意义及用法。
2.会做相应的习题。
◎ 主语从句的考试要求
能力要求:掌握/应用
课时要求:4
考试频率:必考
分值比重:8
◎ 主语从句的所有试题