宜用某种关系代词的情况
指物时，宜能用that的情况（6点）
①当先行词是不定代词时，比如all ,few, little, much, every, something, anything, everything, none, no, one, any, some, any, nothing …等，关系代词只能用that
Is there anything that I can do for you?
All the people that are present burst into tears
②如果先行词有序数词、形容词最高级或the last, the only修饰时
This is the most interesting film that I have ever seen.
The Yangtze River is the second longest river that exists in the world.
③当先行词有very, right, only, same修饰时，表示“仅仅”，“就是”，“正是”等
This is the very/right book that I am looking for. 这正是我在找的那本书。
This pen is the only tool that you can use here. 你仅能使用的工具是钢笔。
④当先行词既指人又有指物的时候
他们正在谈论他们在上海所遇到的人和事。
They are talking about the persons and things that they met in Shanghai.
⑤避免重复。凡是who开头的句子，后面有定语从句时，用that而不是who；
凡是which开头的句子，后面有定语从句修饰物时
Who is the lady that is speaking French there?
Which is the pencil that you used just now?
⑥在there + be 的句型中或当先行词或者关系代词作从句表语时，常用that
There are two novels that I want to read.
Tom is not the person that he used to be.
指物时，只宜用which的情况(6点)
介词前置,指物时,必须用which
在非限定性定语从句中指物时, 必须用which
My borrowed pen, which is John’s, is missing.
在非限定性定语从句中,修饰整个句子.
He failed in the test, which made his teacher very unhappy
与as区别：前面发生的事产生后面结果用which
当关系代词后面带有插入语时
Here is the English grammar which, as I have told you, will help improve your English.
避免重复
当先行词为that时
或一个句子中有两个定语从句，其中一个用了that，另一个宜用which
That which you borrowed is out of date.
I bought some magazines that might help me to kill time and which I could pass on to others when I finished them.
当指人的身份、特征时
He is cheerful, which is his finest trait.
指人时，宜用who的情况（4点）
非限定性定语从句中指人的时候，只能用who
避免重复。如先行词为that/those时
如果先行词是one, ones, anyone, anybody, everyone, everybody, someone, somebody时,关系代词应该用 who 或whom
There be结构中，修饰主语的定语从句宜用who
There’s a gentleman who wants to see you. |
