It was quite a long time before he realized his mistake.before he realized his mistake是什么从句

问题描述:

It was quite a long time before he realized his mistake.
before he realized his mistake是什么从句

当他认识到自己的错误时,已经过相当长的时间。

状语从句

很长时间以后他才意识到自己的错误.
It is/was +时间段+before....多长时间以后,才...
it is/was not+时间段+before...多长时间以后,就.
时间状语