(2)whose的用法：一般指人，有时也指物。在定语从句中作定语。 
例如：I have got a friend whose brother is training for the Olymoics.
(3)which的用法：一般指物，在定语从句中作主语、宾语、偶尔作定语。 
例如：The photo which we liked best was taken by Zhao Min. 
(4)that的用法：指人或物，指人时可与who、whom互换，指物时可与that互换。
在从句中可作主语、宾语，还可作表语。 
例如：It is a book (that/which) no one really likes. 
4. 宜用who不宜用that的情况 
(1)先行词是指人的不定代词时 
例如：Congratulations to our winners and thanks to everyone who entered the competitions.  
(2) 先行词指人时且含有较长的后置定语     
例如：The boy was crying hard who lost his way while looking for his mother.
5. 在以下情况中，关系代词常用that
(1)先行词为all, little, few, none 及some-, any-, no-与thing所组成的复合单词时，只能用that。
例如：There is nothing that will stop us making progress. 
(2)先行词前有only, some, any等形容词修饰时，只能用that。
例如：This is the only problem that we can’t work out.
(3)先行词前由形容词的最高级或序数词修饰时，只能用that。
例如：This is the most interesting book that I have ever read.
(4)先行词同时包括人和物时，只能用他和她，
例如：Lu Xun and his works that we are familiar with are considered great.
6. 只能用which不能用that的情形
(1)当非限制性定语从句中的先行词指物时，只能用which
例如：The pencil-case, which I bought last week, is missing.
(2)关系代词前面有介词时，只能用which
例如：The tree under which we used to take a rest has been cut down.
(3)先行词本身就是that时
例如：I don’t like that which he did.

关系副词的用法 
1. when的用法：它的先行词通常是time, day, morning等。有时也可和一些介词一起引导定语从句。
例如：Do you remember the time when she went abroad?
2. where的用法：它的先行词通常有place, spot, room等。
例如：I like places where the weather is always warm.
3. why的用法：它的先行词只有reason。Why时常也可以省略。
例如：Tell me the reason why she was late.