Question

怎么分析关系代词在定语从句中做主语，宾语.状语 啊，它做谁的主语、宾语啊。是先行词么。。。

Answer 1

楼主真可爱。冲着你那句“我挺笨的”我就帮你仔细分析一下。

我们可以把定语从句断为两部分，一个是主句，就是关系代词之前的句子，一个就是从句。

比如
1 math is a subject which is very difficult to learn 主
math is a subject
A subject is very difficult to learn which 指代的就是subject 即先行词。断开后我们发现A subject在第二句里不就是主语了吗？

2 apples are the fruit which she likes best 宾
同理 she likes the fruit best 不是出来了吗？宾语，like谓语动词后面的

3 the factory where his father works is in th east of th city
这句和前面两句稍微不同
thecity is in the east of th city
his father works in the factory
这时候注意了 where等于 in the factory 可以从他们的性质来看，都是状语。
所以where作从句的状语，从句中主谓齐全。

Answer 2

关系代词引导定语从句，充当定语从句中的主语、宾语、定语、表语，它作的是定语从句中的主语、宾语、定语、表语。（关系代词不作状语）
怎么分析？
把定语从句单独列出，去掉引导词，定语从句中缺少哪个成分，就是引导词充当。可以考虑替换成先行词。
例1 I found the book （which/that） my father bought me.
my father bought me （which宾语，可省略，替换成the booy)
例2 The teacher is looking for the boy who has helped him.
(who主语不可省略，替换成the boy) has helped him.
例3 The girl whose father is a teacher is fond of reading.
（whose定语，属于先行词的，替换成the girl's） father is a teacher
例4 He doesn't seem to be the man (that) he was ten years ago.

引导词作表语不太常见。一般用that
he was (that表语,替换成the man) ten years ago