教我分析英语从句中,哪个是主句哪个是从句的问题?

从句的作用就是充当主句的成分.通常情况下从句前面有引导词.(that what who where之类的).最简单的办法就是找引导词.引导词后面的就一定是从句.但是如果想彻底搞清这个问题,你要先学会分析简单句的句子成分.然后再进一步分析复杂句中,主句少什么成分,从句就是充当什么成分.
下成这几个例子是不同的从句.已经把从句用刮号标出了.
表语从句：This is (what I want to know).
宾语从句：He was afraid (that his baby would touch that cat).
定语从句：I want to have the book (that you have bought yesterday).
状语从句：She turned on TV set and sit down (when a thief came into her room).
同位语从句：We have learned the news (that our friend won the game).