one year为时间状语

Inequalities due to environmental factors must be overcome by some form of preschool preparation at least one year for all and two or  even three for some.

参考译文：由于环境因素引发的不平等必须通过某种形式的学龄前准备工作来进行克服，而且对所有人来说至少需要一年的时间，其中有些人至少需要两年甚至三年时间。