It was yesterday that I met your father in the street．

②不管被强调部分是哪种状语，只能用that连接，不得使用where、when等连词.

It was in the street that I met your father yesterday

③被强调部分为人时，可用who(主格或宾格)和whom(宾格)代替that，用that也行。

It was your father that/whom /who I met in the street yesterday

④强调句中 也要注意主谓一致、人称一致和否定转移的问题。

It is they who are our friends．

⑤ It is not until + 被强调部分 + that ...

该句型也是强调句型。主要用于强凋时间状语，译成汉语＂直 到．．．才．．．＂，可以说是 not ... until ... 的强调形式。

⑷.It 的其它句型：

①. It is .... since ....

It is ( has been ) 5 years since his father died.

②. It is ... when .... "当．．．的时候，是．．．"　

It was 5 o'clock when he came here.

③. It be ... before ... .

该句型主句中的 it 指时间， 主句中的时态常是一般将来时或过去时两种时态．主句中的表语多是long， not long ， 3 days ， 2 weeks 等表示时间段的词或短语。

It was 3 days before he went to Beijing.