今天主要是It作形式主语常用的固定搭配，日常口语也经常用到。

It+be+形容词+that从句

It is necessary that... 有必要...

It is important that... 重要的是...

It is obvious that ... 很明显

It is strange that ... 奇怪的是

It is likely that... 可能是...

It is true that ... 诚然...

例句：

It is obvious that he is not a liar but a truth seeker.

很明显他不是一个 说谎的人而是一个真相探索者。

It+be+-ed分词+that从句

It is believed that... 人们相信...

It is konwn to all that... 众所周知...

It has been decided that ... 已经决定...

It must be pointed out that ... 必须指出的是...

It is to be discussed that... 有待讨论...

It is said that ... 据说...

例句：

It has been decided that the book be revised.

已经决定这本书要修改。

It+be+名词+that从句

It is common knowledge that... ...是常识

It is a surprise that... 令人惊奇的是...

It is a pity that ... 遗憾的是...

It is no wonder that... 不足为奇的是...

It is a mystery that ... 令人神秘不解的是...

例句：

It is common knowledge that the earth moves round the sun.

地球围着太阳转这是常识。

It+be+不及物动词+that从句

It happens that... 碰巧...

It occurred to me that... 我突然想起..

It turned out that ... 结果是...

It seems/appears that... 好像是...

例句：

It occurred to me that he had left his card at home.

我突然想起他把卡落在家里了。