十四、复合句——名词性从句

　　一个句子起名词的作用，在句中做主语、宾语/介词宾语、表语、同位语，那么这个句子就是名词性从句。

　　1.what/whatever的用法

　　考生应把握：what是关系代词，它起着引导从句并在从句中担当一个成分这两个作用。如：

　　They lost their way in the forest, and what made matters worse was that night began to fall.

　　(what既引导主语从句又在从句中做主语)

　　Water will continue to be what it is today—next in importance to oxygen.

　　(what既引导表语从句又在从句中做表语)

　　2.whoever和whomever的区别

　　whoever和whomever相当于anyone who，用主格与宾格取决于其在从句中做主语还是做宾语。如：

　　They always give the vacant seats to whoever comes first.

　　(whoever在从句中做主语)

　　3.有关同位语从句的问题

　　(1)下列名词常用做同位语的先行词：

　　appeal, belief, conclusion, condition, conviction, doubt, evidence, fact, fear, feeling, ground(s),hope, idea, likelihood, message, news, opinion, order, plan, point, possibility, problem, promise,reply, proof, proposal, question, rumor, sign, story, suggestion, suspicion, theory, thought, truth, trouble, understanding, worry。如：

　　I have no doubt that he will overcome all his difficulties.

　　One sign that you are making progress in an art such as painting or photography is that you begin to realize how much there is to learn.

　　(2)引导词通常为that, 但有时因名词内容的需要，也可由whether及连接副词why, when, where,how引导。that不表示任何意义，其他词表示时间、地点、原因等。如：

　　The problem, where I will have my college education, at home or abroad, remains untouched.

　　The fact that she was a few minutes late is no reason for discharging her.

　　(3)同位语从句有时与先行词隔开，注意识别。如：

　　Evidence came up that specific speech sounds a

　　re recognized by babies as young as 6 months old.

　　(4)同位语从句与定语从句的区别：

　　● 从意义上看，同位语从句说明名词的具体内容，定语从句则对名词进行限定、修饰;

　　● 从结构上看，同位语从句的引导词不在从句中充当任何语法成分，定语从句的引导词在从句中必须充当一定的句子成分;

　　● 从先行词的词义特点看，同位语从句的先行词表达的是抽象内容，这类词数量有限，而定语从句的先行词则没有任何限制。

　　4.whether与if在引导名词性从句时的区别

　　(1)主语从句只能用whether引导;

　　(2)whether一般多用于宾语从句的肯定式，而if引导的从句可以有否定式;

　　(3)whether or not可以连在一起用，而if or not则不能，or not只能放在句末;

　　(4)whether可以引导介词宾语从句，if则不能;

　　(5)宾语从句提至谓语前面时，只能用whether引导;

　　(6)在question, ask后面一般只用whether，question的同位语从句也用whether引导;

　　(7)后接不定式时，只能用whether。

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