i think parents should first help their kids (这里为什么没有to)know study is

问题描述:

i think parents should first help their kids (这里为什么没有to)know study is
what they should be(为什么有be)doing?

那个to可以省略.should是情态动词后面要跟动词原形,be是are的原形,所以要用be.而且 be doing表示现在进行时,这里用的就是这个语法.