人教新课标选修八unit1单元语法讲解：名词性从句

人教新课标选修八unit1单元语法讲解：名词性从句,http://www.i3xuexi.com

    名词性从句
    在句子中起名词作用的句子叫名词性从句。名词性从句的功能相当于名词词组,它在复合句中能担任主语、宾语、表语、同位语、介词宾语等, 因此根据它在句中不同的语法功能,名词从句又可分为主语从句、宾语从句、表语从句和同位语从句。

    主语从句的用法
一. 主语从句在复合句中作主语, 它可以位于句首, 但常见的主语从句多放在句末,句首则用形式主语it。
1. That the earth is round is true.         
     = It is true that the earth is round.
2. Whether he will come hasn’t been decided.
     = It hasn’t been decided whether he will come.
注意: 连词that, whether在从句中不担任句子成分,只起连接作用,不能省略  (注:if不可用来引导主语从句）
二. 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 (多用 should)
     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…
      It appears that…     似乎…
(4) It is ＋ 过去分词＋从句
      It is reported that…   据报道…
      It has been proved that… 已证实…
      It is said that…   据说…
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/whom。例如:
判断:
     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.
It is John that broke the window www.i3xuexi.com

    宾语从句的用法：
句子结构：
主句 + 连接词(引导词) + 宾语从句
连接词:从属连词that, whether, if
                  连接代词 Who, whom, whose,which, what   
                连接副词 where, how, why, when
一. 连词 (引导词)
1. 当宾语从句是陈述句时(包括肯定句和否定句), 连词由that引导, 因为that在从句中不作任何成分, 也没有任何具体意思, 因此在口语或非正式文体中常省略。
 Jane said (that) she wasn’t late for the meeting.
2. 当宾语从句是特殊疑问句时, 由特殊疑问词充当连接词, 因为该特殊疑问词(即连接词)在从句中担任一定的句子成分, 具有一定的意义, 所以不可以省略。
Do you know what he said just now?
I don’t remember when we arrived
3. 当宾语从句是一般疑问句时,由连词whether或if引导(口语中常用if),因为if/whether翻译成是否,具有一定的意义,所以不能省略。
   Lily wanted to know if /whether her grandma liked the handbag .
   Let’s see if /whether we can find out some information about that city
注意:
① 关联词只能用whether不能用if 表示 “是否”的情况如下：
   A) 在表语从句和同位语从句中。如：
        The question is whether the film is
   worth seeing.
        The news whether our team has
   won the match is unknown.
B) 在主语从句中，只有用it 作形式主语时, whether和if 都能引导主语从句, 否则, 也只能用whether。如:
     Whether we shall attend the meeting hasn’t been decided yet.
     It hasn’t been decided whether (if) we shall attend the meeting.
C) 在介词之后。(介词往往可以省略) 如:
     It all depends (on) whether they will support us.
D) 后面直接跟动词不定式时。如：
　 He doesn’t know whether to stay or not.
E) 后面紧接or not 时。如：
　 We didn’t know whether or not

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