由连接代词what，who，whoever，which引导 Who will attend the meeting is not important.

谁将参加会议不重要。

What you need is more experience.

你需要的是更多的经验。 由连接副词when，where，how，why引导 Why he failed the English exam wasn't clear.

他英语考试失败的原因不清楚。 用it作形式主语 It is a pity that you have made such a foolish mistake.

很遗憾你犯了如此愚蠢的错误。

It hasn't been decided where she will spend her holiday.

她将去哪儿度假还没确定。 　　2.应注意的问题：

　　(1)注意同强调句型的区别

　　It is a pity that you didn't go to see the film.

　　太遗憾了，你没去看电影。

　　It was in the morning that the murder took place.

　　谋杀发生在早晨。

　　(2)用it作形式主语的结构

　　①It is＋名词(good news/an honor/a pity/a shame/no wonder/common knowledge)＋that从句

　　It is a pity that you have to leave so soon.

　　你这么快就要离开真是遗憾。

　　②It is＋形容词(obvious，possible，likely，strange，probable，doubtful，certain，etc.)＋that从句。

　　It is certain that prices will go up.

价格将会上涨是确定的。