一、引導(dǎo)表語的有that,whether,what,who,when,where,because,why,as if,as though以及as。

1、that引導(dǎo)表語從句

結(jié)構(gòu)：The fact/truth/chance/result/reason/cause+is that,其中that不做成分，可以省略。

2、whether引導(dǎo)表語從句

在表語從句中，需表示是否之意時，只能使用引導(dǎo)詞whether而不能用if

3、連接代詞（what,who等）和連接副詞（when,where,how）引導(dǎo)的表語從句，語序應(yīng)該為陳述句語序、非疑問句語序，而且這些連接代詞和連接副詞在句子都作成分。

The town is no longer what it used to be

4、because和why引導(dǎo)表語從句

主要區(qū)別在于because用于結(jié)果已于前述，需要補敘原因時，也即“先果后因”的倒敘法；why則用于原因已于前敘，需進一步說明其結(jié)果的情況，也即“先因后果”的倒敘法。

He didn't come to school yesterday that was because he was ill.

還有一些固定用法：（1）The reason why .....is that....(2)The cause is that....

5、as if/though引導(dǎo)表語從句

在look,seem,appear,feel,smell,sound,taste等系動詞之后?？山佑衋s if/though引導(dǎo)的表語

It seems as if it will to rain.

6、as引導(dǎo)表語從句

The main reasons are as follows.

二、語氣問題

1、在由as if/though 引導(dǎo)表語從句中，若其內(nèi)容是一種假設(shè)或與事實不符，則需要用虛擬語氣

The elephant feels as if it were a wall.

2、當(dāng)suggestion,order,proposal,demand名詞后接表語從句時該從句謂語動詞多用should+動詞原形，其中should可省略。

Their suggestion is that our choice(should) be incorrect.