请问,强调句中（it is/was.that/who）除了is/was,be还可以采用什么形式?

强调句的固定结构是it 引导的句子.
It is (was) 被强调部分+ that (who) + 句子其他部分.
此结构强调的成分仅限于主语,宾语和状语.
It is from the sun that we get light and heat.
It was not until I had read your letter that I understood the true state of affairs.
这是个约定俗成的句型,谓语只有 is/was 这两种时态表示.