讲义
如果句子的主词是that子句，可用it代替，再把that子句移到后面。

That the earth is round is true. = It is true that the earth is round.

地球是圆的是真的。

That you can not come to my wedding is a pity.

= It is a pity that you can not come to my wedding.

你不能来参加我的婚礼太遗憾了。

It's a bad habit that John goes to bed without brushing his teeth.

John每天不刷牙就上床睡觉真是个坏习惯。

如句中有how, when, where, why,或whether等疑问词所引导的子句，也可以用it代替，再把子句移到后面。

How he escaped from jail is unknown.

= It is unknown how he escaped from jail. 没人知道他是怎么越狱的。

Why she was killed is still a puzzle.

= It is still a puzzle why she was killed. 她的被害仍然是个谜。