(1) 结构：It is / It was (过去时间) + 被强调部分 + that / who (专指人) + 其他部分
(2) 用法：除了谓语动词不能强调，句子的每部分均可强调。 Jim met the student in the street last week.
主语 宾语 地点状语 时间状语
强调主语：It was Jim who / that met the student in the street last week.
强调宾语：It was the student whom / that Jim met in the street last week.
强调地点状语：It was in the street that Jim met the student last week.
强调时间状语：It was last week that Jim met the student in the street.
Was it Dr Wang who spoke to you just now?
Who is it that will visit our class?
Where is it that he has gone?
When was it that she went?
not … until … 用于强调句：
It was not until then that I realized I was wrong.