名词性从句Noun clauses 名词性从句是由 if, whether, that 和各种疑问词充当连接词所引导的从句，其作用同名词一样。包括 主语从句，宾语从句，表语从句和 同位语从句。一．主语从句 主语从句是在复合句中充当主语的从句，通常放在主句谓语动词之前或由形式主语 it 代替，而本身放在句子末尾。1. It 作形式主语和 it 引导强调句的比较It 作形式主语代替主语从句，主要是为了平衡句子结构，主语从句的连接词没有变化。而 it引导的强调句则是对句子某一部分进行强调，无论强调的是什么成分，都可用连词 that 。被强调部分指人是也可用 who 。例如： It is a pity that you didn’t go to see the film. It doesn’t interest me whether you succeed or not. It is in the morning that the murder took place.(=In the morning the murder took place.) It is John that broke the window.(=John broke the window.)2. 用 it 作形式主语的结构(1) It is ＋名词＋从句 It is a fact that … 事实是… It is an honor that …非常荣幸 It is common knowledge that 是常识(2) It is ＋形容词＋从句 It is natural that… 很自然… It is strange that… 奇怪的是…(3) It is ＋不及物动词＋从句 It seems that… 似乎… It happened that… 碰巧…(4) It ＋ is/was+ 过去分词＋从句 It is reported that… 据报道… It has been proved that… 已证实…It is said/thought/hoped/told/believed +that….3. 主语从句不可位于句首的五种情况 (1) It is said , (reported) … 结构中的主语从句不可提前。例如：It is said that President Bush will visit our country next week. (right)That President Jiang will visit our school next week is said. (wrong)(2) It happens that.., It occurs that… 结构中的“ that” 从句不可提前。例如：It occurred to him that he failed in the examination. (right)That he failed in the examination occurred to him. (wrong)(3) It doesn’t matter how/whether … 结构中的主语从句不可提前。例如：It doesn’t matter whether he is wrong or not. (right)Whether...
