It's time_____school.A.to B.for C.from D.of

B
It's time for + n.的固定搭配

B.for

应该是B吧，有点搅混乱了。。。。

B.

It's time for sth.
如:It's time for lunch.是时候吃午饭了.

It's time to do sth.
如:It's time to go to bed.是时候睡觉了.
It's time to go to school.是时候该上学了.