关于英语强调句（新概念3册21课）It is...that..

二．强调句的人称,时态,数的运用.
强调句的时态依原句而定.
原句的时态为过去的某种时态,
则强调句中的be就用过去时
was.
原句为现在的某种时态,
强调句中就用be的现在时态.
有时还可用It might be／must have been／can’t be ...that...
等句型.

It is Jack who loves football most.(is 与loves时态一致)
It was because I was stuck in the traffic that I came
late(was 与came时态保持一致)
It might be tomorrow morning that the news will be broadcast.
Tips:
被强调部分为主语时,
that／who后面的谓语动词在人称和数上应和句子的主语相一致.如：
It is I that／who am your friend that hill come to help you.