It is their dream to have a bridge.为什么要有一个“it is”?

问题描述:

It is their dream to have a bridge.为什么要有一个“it is”?

哪,去掉it的话呢,就是To have a bridge is their dream。

强调句吧。

这是it做形式主语,is是系动词,their dream做表语,后面的 to have a bridge是动词不定式做真正的主语的句型.
强调句的构成形式应该是it is/was + 被强调部分 +that/who +其他成分

起强调作用