3. It+及物动词（被动语态）+主语从句

It has been decided that the exhibition will not open on Sundays.

现经决定展览会星期日不开放。

【注意】

　　(1) 主语从句在句首时，必须由连接词引导，不能省略这些连接词；但是如果用it作形式主语，而把主语从句放在句末时，从属连词that可以省略。

他们相互喜爱是很自然的。

误: They should like each other is natural.

正: That they should like each other is natural.

正: It is natural (that) they should like each other.

　　(2) 如果主语从句放在句首，不能用if引导；但是如果用it作形式主语，而把主语从句放在句末时，也可以用if引导。

玛丽是不是真听见他了，很值得怀疑。

误: If Mary really heard him is really doubtful.

正: Whether Mary really heard him is really doubtful.

正: It was doubtful whether/if Mary really heard him.

The fact is/It is a fact that...

【即学即练】

1. I have always been honest and straightforward, and it doesn't matter ___________ that I'm talking to.

　A. who is it B. who it is C. it is who D. it is whom

2. It is pretty well understood ___________ controls the flow of carbon dioxide in and out the atmosphere today.

　A. that B. when C. what D. how

3. __________ made the school proud was ___________ more than 90％ of students had been admitted to key universities.

　A. What; because B. What; that C. That; what D. That; because

4. __________ team wins on Saturday will go through to the national championship.