强调句可以强调句子中除谓语外的任何部分,并且去掉(It+was/is+who/whom/that)这个结构后句子仍能成立.
例:All the members held a meeting in the club yesterday.
（强调all the members） It was all the members that held a meeting in the club yesterday.
（强调a meeting ）It was a meeting that all the members held in the club yesterday.
（强调in the club ）It was in the club that all the members held a meeting yesterday.
（强调yesterday）It was yesterday that all the members held a meeting in the club.
It 作形式主语代替主语从句,主要是为了平衡句子结构,主语从句的连接词没有变化.而it引导的强调句则是对句子某一部分进行强调,无论强调的是什么成分,都可用连词that.被强调部分指人是也可用who/whom.主语从句：It is +形容词/名词/某些动词ed + that 从句.