表语从句两大问题

1、that引导表语从句

结构：The fact/truth/chance/result/reason/cause is that,其中that不做成分，可以省略。

2、whether引导表语从句

在表语从句中，需表示是否之意时，只能使用引导词whether而不能用if

3、连接代词（what,who等）和连接副词（when,where,how）引导的表语从句，语序应该为陈述句语序、非疑问句语序，而且这些连接代词和连接副词在句子都作成分。

The town is no longer what it used to be

4、because和why引导表语从句

主要区别在于because用于结果已于前述，需要补叙原因时，也即先果后因”的倒叙法；why则用于原因已于前叙，需进一步说明其结果的情况，也即先因后果”的倒叙法。

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

还有一些固定用法：

（1）The reason why .....is that....(2)The cause is that....

5、as if/though引导表语从句

在look,seem,appear,feel,smell,sound,taste等系动词之后常可接有as if/though引导的表语

It seems as if it will to rain.

6、as引导表语从句

The main reasons are as follows.

1、在由as if/though 引导表语从句中，若其内容是一种假设或与事实不符，则需要用虚拟语气

The elephant feels as if it were a wall.

2、当suggestion,order,proposal,demand名词后接表语从句时该从句谓语动词多用should 动词原形，其中should可省略。

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