主语从句 一、主语从句的连词分三类 （1）从属连词引导的主语从句 （that whether if） that 引导的主语从句:引导词 that 无含义/在句中不做成分/不可以省。That 引导主语从句通常用 it 作形式主语。 例如：That you will win the medal seems unlikely. That she survived the accident is a miracle. whether 引导的主语从句: whether 有含义(是否)/在句中不做成分/不可以省。 注意：引导主语从句，不能用 if 不能在开头，只能用 whether。 Whether we will hold a party in the open air tomorrow depends on the weather. Whether she is coming or not doesn’t matter too much. （2） 用连接代词引导的主语从句 在由连接代词 who, whose, whom, which, what, whoever, whomever, whichever, whatever 引导的名词性从句中，其连接代词在句中起名词性作用，担当一定成分. 例如：What you need is more practice. Whatever we do is to serve the people. 注：whatever / whoever 的功用 whatever, whoever 在主语从句中不含疑问意义。它引导主语从句，并在从句中作主语、宾语、表语等。 whatever = anything that; whoever = anyone who。要注意和 whatever, whoever 引导的让步状语从句的区别。 如：Whoever breaks the law should be punished. （主语从句） （ ＝Anyone who breaks the law should be punished. ） Whoever breaks the law, he should be punished. （让步状语从句） （ ＝No matter who breaks the law, he should be punished. ） （3）用连接副词 when, where, why, how 引导的名词性从句(其连接副词有含义,在句中作状语。) 例如:Where we should leave it is a problem. When they will come hasn’t been made pubic. 三、it 作形式主语的主语从句 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。这分四种情况： (1 ) 对于以连词that 引导的主语从句，通常用形式主语it 替代主语从句：
It is +名词+从句 It is a fact that… 事实是……；It is good news that … ……是好消息；It is a question that … ……是个问题；It is common knowledge that … ...
