Anticipatory it

it用來充當形式主語或形式賓語，后面的真正主語或真正賓語通常是不定式結構、動名詞或名詞性分句。It的這種用法叫作先行it。

eg.
It is quite important for us to form a good studying habit.
I think it important to finish the task in time.

it用來充當形式主語，后置的真正主語往往可以取代先行it的位置，出現在句首。
Eg. To form a good studying habit is quite important for us

并非所有先行it結構都可轉化，下邊句子只能作如下轉化。
eg.
It seems that John is not coming after all.
John doesn’t seem to be coming after all.

Cleft it :

Task
1. 句子的基本結構
2 .分裂句的本質
3 . 分裂句的結構
4 .假擬分裂句

句子結構
主語+謂語
已知信息
新信息
末端中心
末端重心
Eg. I told him the news yesterday.

分裂句的本質
Eg. I told him the news yesterday.
Eg. It is I that told him the news yesterday

分裂it

分裂句是以it為引導詞的強調句型。它的結構形式是：It +be 的一定形式+中心成分＋that /who分句。通過這種結構可以強調除謂語動詞以外的大多數句子成分。說話人通過分裂句分別強調主語、間接賓語、直接賓語、狀語，使之成為信息中心。分裂句中的謂語可以采取復雜形式

Eg.
It is I who am to blame.
It may have been at Christmas that John gave Mary a handbag.
It was in Shanghai that I got my Master’s Degree.

主語補語通常不作分裂句的中心成分。賓語補語可以這樣用。
*It is beautiful that she is.
It is Chairman of the committee that they elected him.