[观察例句]
1．Our guide，who was a French Canadian，was an excellent cook.
2．Peter，whom you met in London，is now back in Paris.
3．The boy，whose hat is red，studies very hard.
4．He will come here yesterday，when he will be free.
5．They went back to London，where was their hometown.
[归纳用法]
1．who引导的非限制性定语从句
My gardener，who is very pessimistic，says that there will be no apples this year.
我家的园丁非常悲观，他说今年将不结苹果。
2．whom引导的非限制性定语从句
Mr.Smith，from whom I have learned a lot，is a famous scientist.
史密斯先生是一位著名的科学家，我从他那儿学了许多东西。
3．whose引导的非限制性定语从句
whose是关系代词who的所有格形式，在从句中作定语。whose通常指人，也可指动物或无生命的事物。
The boy，whose father is an engineer，studies very hard.
那个小男孩学习很努力，他的父亲是位工程师。
The house，whose windows face north，belongs to him.
窗子朝北的那个房子是他的。
4．which引导的非限制性定语从句
关系代词which在非限制性定语从句中所指代和修饰的可以是主句中的名词、形容词、短语、其他从句或整个主句，在从句中作主语、动词宾语、介词宾语或表语。
(1) which指代主句中的名词，被指代的名词包括表示物、婴儿或动物的名词、表示单数意义的集体名词以及表示职业、品格等的名词。
These apple trees，which I planted three years ago，have not borne any fruit.
这些苹果树是我三年前栽的，还没有结过果实。
(2)which指代主句中的形容词。
She was patient，which her husband seldom was.
她有耐心，她丈夫却很少这样。
(3)which指代主句中的某个从句。
He said that he had never seen her before，which was not true.
他说以前从没见过她，这不是真的。
(4)which指代整个主句。
In the presence of so many people he was little tense，which was understandable.
在那么多人面前他有点紧张，这是可以理解的。
