英语四六级考试语法备考指导：名词性从句

　　(二)同位语从句前名词的数

　　同位语从句前的名词通常用单数形式，并且往往带有限定词(word除外)加以修饰。例如：

　　Where did you get the idea that I could not come?

　　Give me your promise that you will come to our party this evening.

　　Word came that China launched its first manned spaceship on October 15, 2003.

　　(三)同位语从句连接词的选用

　　1. 在英语中，引导同位语从句的词通常有连词(that, who, whether)，连接副词(how, when, where)等。

　　They were all very much worried over the fact that you were sick.

　　The question who should do the work requires consideration.

　　We haven’t yet settled the question where we are going to spend our summer vacation.

　　2. 表示“是否”的意思时只能用whether，不能用if。这一点与主语从句相似。例如：

　　The question whether he can finish the work within two days remains unknown.

　　3. 在名词doubt“怀疑”后的同位语从句用whether连接;在no doubt“不怀疑”之后的同位语从句用that连接。例如：

　　We have some doubt whether they can complete the task on time.

　　There is no doubt that Zhang Wei will keep his promise.

　　(四)同位语从句与定语从句的用法区别

　　(1)词类不同

　　同位语从句的名词只能是前面提到的几个有限的、有一定内涵的名词;而定语从句的先行词可以是名词、代词、主句的一部分或是整个主句。

　　(2)性质不同

　　定语从句是从句对其先行词的修饰或限制，属于形容词性从句的范畴;而同位语从句是从句对其前名词的解释，该名词与同位语从句的关系可以用“主系表”来表达。例如：

　　We have all heard the news that our team has won.

　　名词与其后的同位语从句可以表达为：

　　The news is that our team has won.

　　(3)引导词不完全相同。

　　A. 有些引导词如：how, whether可以引导同位语从句，但不能引导定语从句。what不可以引导定语从句，但却可以引导同位语从句。例如：

　　I have no idea what has happened to him.

　　B. 引导词that引导定语从句时，在从句中一般作主语或宾语，(指物时还可用which代替)，如果在从句中作宾语常可以省略。that在同位语从句中虽不充当任何句子成份，但不能省略，也不能用which来代替。例如：

　　<1>The order that we should throw away our luggage was received yesterday.

　　<2>The order(that)we received yesterday was that we should throw away our luggage.

　　通过比较可知：第<1>句中的划线部分是对名词order的具体解释，that只起到连接作用，但不能省;第<2>句中的划线部分是名词order的修饰语，that代指the order，在从句中充当宾语，因而在句中可以省略。