表语或同位语。

1、引导词what与that的用法区别。

引导主、宾、表语从句时，what要充当主语、宾语或表语等句子成分，that不作任何成分，只在语法上起连接的作用。例如（NMET'96）：

____ we can't get seems better than ____ we have.

A. What; what B. what; that C. That; that D. That; what (答案A )

That the former Iraq president Saddam was captured has been proved.

2、引导词whether和if的用法区别。

通常，引导主语从句、表语从句和引导同位语从句时，要用连词whether，不用if；习惯上也只能说whether or not，而不说if ...or not。例如（MET92）：

____ the 2000 Olympic Games will be held in Beijing is not known yet.

A. Whenever B. If C. Whether D. That (答案为C)

　　3、名词性从句的语序。

与别的从句一样，名词性从句必须用自然语序，即使在疑问句中，从句也不倒装（而在主句上倒装）。例如（MET91）:

No one can be sure ____ in a million years.

A. what man will look like B. what will man look like

C. man will look like what D. what look will man like (答案为A)

4、Who / whoever, what / whatever等的用法区别。

一般说来，what/who等含特指意义，而whatever/whoever等含泛指意义，意为"无论什么/无论谁"。例如（NMET97）：

It is generally considered unwise to give a child ____ he or she wants.

A. however B. whatever C. whichever D. whenever (答案为B)

　　5、Where, when, why等连接副词引导的名词性从句。

Where, when, why等连接副词也可以引导名词性从句，使用的关键是：这个词必须符合句子的逻辑要求。例如（NMET'99）：

- I drove to Zhuhai for the air show last week.

- Is that ____ you had a few days off?

A. why B. when C. that D. where (答案为A）

6、同位语从句引导词where, when的用法特点。