请问：怎样判断定语从句、主语从句和表语从句
问题描述：
请问：怎样判断定语从句、主语从句和表语从句
请说的通俗易懂点.
答
1.主语从句是一个从句作主语
比如:Where a person comes from will affect their style of speech.
由that,which,whether,where,what,how,when,why,and so on引导的从句做主语,就是主语从句
2.当从句在表语的位置时,就是表语从句
比如／：That is why English is a language with so many confusing rules.
3.定语从句就比较烦,也比较多
比如／：This is the plan he told me
首先要有先行词,先行词后面那个词等于先行词,同时在后面的从句中做成分,在做宾语时that,which可以省略．