㈠ It is/was...who/ that...句型
这是一个最常见的强调句型。利用这种句型可以强调除谓语动词外的大多数句子成分，所强调的可以是单词、短语，也可以是从句，但结构必须完整。被强调的成分可以是主语、宾语和状语，但不能是定语或谓语。引导词it置于句首，后接动词be(一般是is或was)，再加上强调的部分，再接that-/who-从句。如：
Jack missed the first lesson yesterday because he was caught in the traffic jam. →
①It was Jack who missed the first lesson yesterday because he was caught in the traffic jam. (强调主语)
