It is/was + 句子被强调部分 + who/whom/that + 句子其他未被强调部分。
如：I met him in the street yesterday.
如果强调主语I，则强调句型为：It was I who/that met him in the street yesterday.
如果强调宾语him，则强调句型为：It was him whom/that I met in the street yesterday.
如果强调地点状语in the street，则强调句型为：It was in the street that I met him yesterday.
如果强调时间状语yesterday，则强调句型为：It was yesterday that I met him in the street.
[一] it 强调句基本构成形式：It is/ was +被强调部分+ who/ that+原句剩余部分
I met him in the street yesterday afternoon.
It was I who/ that met him in the street yesterday afternoon.
It was him who/ that I met in the street yesterday afternoon.
It was in the street that I met him yesterday afternoon.
It was yesterday afternoon that I met him in the street .
强调句的一般疑问句：Is/ Was it +被强调部分+ who/ that+原句剩余部分
Was it him that/ who you met in the street yesterday afternoon?
What/ When/ Where/ Who/ How……is/ was it + who/ that+原句剩余部分
1). Who was it that/ who you met in the street yesterday afternoon?
2)Ann Peters' husband rushed her to a nearby hospital last night.
主语 宾语 状语
It was Ann Peters' husband that (who) rushed her to a nearby hospital last night.
It was her (she) that (who) Ann Peters' husband rushed to a nearby hospital last
It was to a nearby hospital that Ann Peters' husband rushed her last night.
It was last night that Ann Peters' husband rushed her to a nearby hospital.
[二].do, did, does 用于强调谓语动词,加强语气
1). He is a good student.--> He does be a good student
2). He helped us yesterday. ? He did help us yesterday.
3). Be careful! ? Do be careful!
[三]. not/ never ……. until 直到…..才
1). The villagers didn’t realize how serious the pollution was until all the fish died in the river.
?It was not until all the fish died in the river that the villagers realized how serious the pollution was. (强调句)