1. 以what等連接代詞引導的主語從句

What you need is more practice. 你需要的是更多的練習。

Whoever wants it may have it. 誰要都可以給他。

同類的連接代詞還有：What, who, whom, whose, which, whatever, whoever, whichever

2. 以that, whether從屬連詞引導的主語從句

It was strange that he had made a mistake. 真奇怪，他竟然錯了。

That we need more equipment is quite obvious. 我們需要更多的設備，這是很明顯的。

Whether he will join us won’t make too much difference.

他是否加入我們，沒有太大的差別。

3. 主語從句的引導詞that什么時候可以省略

當主語從句不太長時，引導詞“that”可以省略

It’s clear (that) he has done his best. 很明顯他已經盡力而為了。

It’s a wonder (that) he didn’t fail. 真奇怪，他沒有失敗。

4. 以when等連接副詞引導的主語從句

When they will come hasn’t been made public. 他們什么時候來還沒有公布。

Where she has gone is not known yet. 她去了哪兒，還不知道。

Why he did it will remain a puzzle for ever. 為什么他做那件事將永遠是個謎團。

5. 虛擬語氣：主語從句

形容詞為necessary, important, impossible, strange, natural, essential時，在“It + be + 形容詞或過去分詞 + 主語從句”中，主語從句要虛擬。

It is necessary that the problem (should) be discussed at once.

立刻討論這個問題很有必要。

It is strange that he (should) have so many friends. 太奇怪了，他有那么多的朋友。

6. 主語從句與強調句的區別

注意事項：

1). 在主語從句中，把It was … that去掉之后，就已經完全不像一個句子了。

2). 在強調句中，把It was … that去掉之后，還基本上像個句子。

3). 主語從句有以下的引導詞：what, who, whom, whose, which, whatever, whoever, whichever

4). 強調句的引導詞只有：that, who。

主語從句：

It was strange that he had made a mistake. 如果把，It was … that 去掉以后，剩下strange he had made a mistake.就不算是句子了。

It is immaterial where or when he goes. 他去何處或者何時去是無關緊要的。

<><>It is said that…, 和It is reported that…這樣的結構，后面接的是主語從句：

It is said that he’s got married. 聽說他已經結婚了。

強調句：

It was she that had been wrong. 錯的是她。(強調主語)如果把，It was … that 去掉以后，剩下she had been wrong.還勉強算的上是一個句子。

It was this novel that they talked about last night. 他們昨晚談論的是這部小說。(強調賓語)

It was in London that I first saw her. 我是在倫敦第一次見到她的。(強調地點狀語)