3. 主语从句不可位于句首的五种情况

(1) if 引导的主语从句不可居于复合句句首。

(2) It is said, (reported) ...结构中的主语从句不可提前。例如：

It is said that President Jingo will visit our school next week. (right)

That President Hu will visit our school next week is said. (wrong)

(3) It happens..., It occurs... 结构中的主语从句不可提前。例如：

It occurred to him that he failed in the examination. (right)

That he failed in the examination occurred to him. (wrong)

(4) It doesn't matter how/whether ...结构中的主语从句不可提前。例如：

It doesn't matter whether he is wrong or not. (right)

Whether he is wrong or not doesn't matter. (wrong)

(5) 含主语从句的复合句是疑问句时，主语从句不可提前。例如：

Is it likely that it will rain in the evening? (right)

Is that will rain in the evening likely? (wrong)

4. What 与that 在引导主语从句时的区别

What 引导主语从句时在从句中充当句子成分，如主语、宾语、表语，而that 则不然。例如：

1) What you said yesterday is right.

2) That she is still alive is a consolation.

二、宾语从句

1. 作动词的宾语

(1) 由that引导的宾语从句（that 通常可以省略）,例如：

I heard that be joined the army.

(2) 由what, whether (if) 引导的宾语从句，例如：

1) She did not know what had happened.

2) I wonder whether you can change this note for me.

(3) 动词＋间接宾语＋宾语从句。例如：

She told me that she would accept my invitation.

2. 作介词的宾语