如何区分定语从句中的先行词在从句的成分？？？？

判定定语从句关系词的基本原则是将先行词（被定语从句修饰的那个名词）带到从句中去，如果从句中缺少状语就用“介词+关系代词”或关系副词引导。
所以理论上例三可改写成
a)The building is Jiangwan Hotel, from which we can see the Pearl River.
或
b)The building is Jiangwan Hotel, where we can see the Pearl River.

例四可改写成
a)The man lives in a small house，around which there are many trees.
或
b)The man lives in a small house，where there are many trees.

但是在实际应用中，因考虑到b)可能造成句意不明，所以大多不用。而非因为做状语或不做状语。

例一例二中所示句子，应该也不可用where引导。原因在于to the building中to用于表示方向，而不是表示“在”，go to school为固定表达，也不宜分开。
例如我们通常不会说：
This is the man for whom we are looking.
而要说
This is the man (whom) we are looking for.