二、it作形式主语

1.that引导的主语从句

（1）It+be+名词+that

It is a good thing that ……是好事情　　　　It is a fact that 事实是……

It is a pity/a shame that 真遗憾……　　　　It is a surprise that 令人惊奇的是……

It is a question that ……是个问题　　　　　It is common knowledge that ……是常识

It is good news that ……是好事情　　　　　 It is one’s belief that 某人认为……

It’s a pity that he didn’t come.很遗憾他没来。

It is a mystery how he is going to do it.他打算如何做是个谜。

（2）It+be+形容词+that

It is certain that 肯定……　　　　　　　　It is important that 重要的是……

It is impossible that 不可能……　　　　　 It is likely that 很可能……

It is obvious/clear that 很明显……　　　　It is surprising that 令人惊讶的是……

It is natural that ……那是自然的　　　　　It is necessary that 有必要……

It is possible that 很可能……　　　　　　 It is strange that 很奇怪……

It is possible that he has stolen the car.很可能他偷了小汽车。

It is certain that he will leave for Beijing tomorrow.明天他肯定要去北京。

It is quite clear that he has read the book.很显然，他读过这本书。

（3）It+be+过去分词+that

It is agreed that 大家同意……　　　　　　It is argued that 大家争论……

It is assumed that 假定……　　　　　　　 It is believed that 大家相信……

It has been decide that 大家决定……　　　It is hoped that 大家希望……

It is （well）known that 家喻户晓……　　 It is reported that 据报道……

It is recommended that 据推荐……　　　　 It is rumored that 谣传……

It is said that 据说……　　　　　　　　　It is suggested that 有人建议……

It is supposed that 大家推测……　　　　　It is thought that 大家认为……

It must be remembered that 务必记住……

It is taken for granted that ……被视为当然

It’s decided that the meeting will start at 8 in the morning.定于明天上午八点开会。

It is suggested that you （should）spend more time in studying English.

你应该花更多的时间学习英语。

【提示】 在以上三种句式中，主语从句用来表示惊奇、不相信、惋惜、理应如此等语气时，谓语动词要用虚拟语气“should+动词原形”，should可以省略。

（4）It+不及物动词+that

It appears that 好像是……　　　　　　　　　It happens that 碰巧是……

It occurs to sb.that ...某人突然想起……　　It seems that 好像是……

It strikes sb.most that 令某人印象深刻的是……

It turns out that 结果是……

It happened that I had no money on me.碰巧我身上没带钱。

It seems that your plan is more practical.你的计划似乎更切实可行。

It appears that everybody is here.Let’s start.看来大家都到了，咱们开始吧。

It turns out that our team has won the game.结果是我们队赢了这场比赛。

It really matters that you haven’t turned up.你没来，这的确很有影响。

It occurred to me that we should get in touch with the manager.

我突然想起我们应该与经理联系。

2.whether引导的主语从句

It makes little difference whether we go or stay.我们去还是留没有多大差别。

It’s not yet settled whether I am going to America.我去不去美国还没定。

It was a problem whether they would support us.他们是否会支持我们还是一个问题。

3.连接代词和连接副词引导的主语从句

It is unknown who has broken the glass.谁打破了玻璃现在还不知道。

It is being investigated what he did last night.他昨天晚上干了些什么正在调查之中。

It is unknown when he was born.他生于何时还不知道。