分别主句与从句：简单而言主句就是问题的中心所在.一个句子的中心意思体现在主句中.所以判断主从关系要从意思入手.
或者根据引导词来看,引导词的后面是从句.定语从句主要修饰名次与代词.主要关系词有;who whom whose which that when where why
表语从句置于连系动词后面做表语.
时间状语从句 when,whenever,while,as,before,after,since,till,once,as soon as,etc.
地点状语从句 where,wherever
原因状语从句 because,since,as,for,now that,etc.
目的状语从句 in order that,so that,that,etc.
结果状语从句 so…that,so that,such…that,that,etc.
条件状语从句 if,unless,as(so)long as,etc.
让步状语从句 though,although,even if,even though,however,whatever,as,etc.
比较状语从句 as…as,so…as,than,etc.
方式状语从句 as,as if,as though,etc.
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条件状语从句中,如果主语是一般将来时,从句要用一般现在时