同学你好，该知识点来自沪江网校《大学英语四级全程备考班【小橙卡专享班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学好，
It is/was...that/who...
该句型常用来强调的句子成分有主语、宾语和状语，但很少用来强调其他成分。

所谓强调，就是通过某种手段把句子的一部分甚至整个句子所表达的信息加以突出、强调。表示强调的手段很多，下面来讲几种常用的吧：
1、陈述句的强调句型：It is/ was + 被强调部分（通常是主语、宾语或状语）+ that/ who（当强调主语且主语指人）+ 其他部分。
如：It was yesterday that he met Li Ping.

2、一般疑问句的强调句型：同上，只是把is/ was提到it前面。
如：Was it yesterday that he met Li Ping?

3、特殊疑问句的强调句型：被强调部分（通常是疑问代词或疑问副词）+ is/ was + it + that/ who + 其他部分？
e.g. When and where was it that you were born?

4.not … until … 句型的强调句 　　
A. 句型为：It is/ was not until + 被强调部分 + that + 其他部分 　　
普通句：He didn't go to bed until/ till his wife came back. 　　
强调句：It was not until his wife came back that he went to bed. 　　
B. 注意：此句型只用until，不用till。但如果不是强调句型，till, until可通用；因为句型中It is/ was not ... 已经是否定句了，that后面的从句要用肯定句，切勿再用否定句了。 　　

5.谓语动词的强调 　　
A. It is/ was ... that ... 结构不能强调谓语，如果需要强调谓语时，用助动词do/ does或did。　　
Do sit down. 务必请坐。 　　
Do be careful when you cross the street. 过马路时，务必（千万）要小心啊！ 　　
B. 注意：此种强调只用do/ does和did，没有别的形式；过去时用did，后面的谓语动词用原形。

常用的强调句结构是it引导的句子，下面再举几个例子：
原句：My father did the experiment in the lab yesterday evening.
强调主语：It was my father who did the experiment in the lab yesterday evening.
强调宾语：It was the experiment that my father did in the lab yesterday evening.
强调时间：It was yesterday evening that my father did the experiment in the lab.（注意不用when）
强调地点：It was in the lab that my father did the experiment yesterday evening.


祝学习进步。