当需要
强调句中的主语，宾语和状语时，常用强调句：it is/was+ 被强调的部分 ＋that/who.
He bought three books in the bookstore yesterday.
强调主语：
It was he that/who bought three books in the bookstore yesterday.
强调宾语：
It was three books that he bought in the bookstore yesterday.
强调状语：
It was in the bookstore that he bought three books yesterday.