it 的三种情况:

it 是代词,代替前面提到的物,“它”;形式主语,代表“事情”; 强调句型中的假主语。

1 it 是人称代词“它”

It is the first major university to tell students that they will not return to campus when the new school year begins.

它是第一所告诉学生开学不能返校的重要大学。

2 it 是形式主语,代表一件事,真正的主语是动词不定式短语

It is wise for the university to tell students that they will not return to campus when the new school year begins.

对于这所大学来说,告诉学生开学不能返校是明智之举。

3 it 是形式主语,代表一件事,真正的主语是that 引导的主语从句

It is wise that the unversity asked the students not to return to campus when the new school year begins.

这所大学告诉学生开学不能返校是明智之举。

4 it 是假主语,强调句型,it is that 都去掉,句子还是完整的

It is the unversitythat asked the students not to return to campus when the new school yearbegins.

告诉学生开学不能返校的正是 这所大学

强调

It is when the new school year beginsthat the unversity asked the students not to return tocampus.

这所大学告诉学生是 在开学时不能返校。