1． It作先行主语和先行宾语的一些句型

She had said what it was necessary to say.

2． 强调句型

It is not who rules us that is important, but how he rules us.

3． "All+抽象名词"或"抽象名词+itself"（very+形容词）

He was all gentleness to her.

4． 利用词汇重复表示强调

A crime is a crime a crime.