引导表语从句的先行词

常见的表语从句引导词总共有五类，连词that，whether，连接代词，连接副词，和关系代词what

一.that

当that引导表语从句时，只起连接作用，不在表语从句中充当任何句子成分,但通常不省略，除了在部分口语句子中。

如：

The fact is that he doesn’t really try.

The trouble is (that) he is ill.

The reason why he didn't come wasthat he missed the train.

二.whether

当表语从句要表达“是否”的含义时，连接词要用whether, 并且绝对不能用if进行替换。

如：The question is whether the film is worth seeing.

三.连接代词who/whom/whose/which

当疑问代词用来连接表语从句时，既起连接作用，又充当句子成分。

如：

The problem is who we can get to ｒｅｐｌａｃｅ her.

The quesstion is whom we can trust.

四.连接副词when/where/why/how

当疑问副词来连接表语从句时，既起着连接作用，同时充当句子成分，一般作状语。

如：

The problem is how we can find him.

That’s why he didn’t come.

五.关系代词what

what引导表语从句时，既起连接作用，又充当句子成分。

如：I am no longer what I was.

That’s what I want to stress。