that 可以是人也可以是物 但是WHICH是物
①先行词是不定代词all,something,anything,everything, none,the one,little,much等时，要用 that/who/whom,而不用 which.
例
All that heard the news was delighted.T
所有听到这个消息的人都很高兴。
Is there anything that I can do for you?
我能为您做点什么？
②先行词前有形容词最高级修饰时，要用that，而不用which。
例
He was the best king that ever ruled the country.
他是曾统治过这个国家的最好的一位国王。
This is the best film that I have ever seen for years.
这是几年来我看到的最好的一部电影。
③先行词前有序数词修饰时，要用that，而不用which。
例
This is the fifth book that I have ever written.
这是我写好的第五本书。
④先行词前有形容词only,very,few,little,no,right等修 饰时，要用that，而不用which。
例
She was the only person that was invited to the Palace.
她是被请进宫里来的惟一一位。
⑤先行词既指人，又指物时，只能使用that。
例
They told about thing and person that they remember at school.他们谈论了他们记起的人和事。
（2）在下列情况下要用 which:
①在非限制性定语从句中。
例
She made great progress and won a prize,which gave us a surprise.她取得了很大进步并获得了奖金，这使我们很惊讶。
Mrs Tailor's cat, which was very old,became ill and then died.泰勒太太的猫很老了，生病以后就死了。
②在介词+关系代词引导的定语从句，必须使用which。
例
This is the knife with which John hurt somebody.
这就是约翰伤人的那把刀。
He built a telescope through which he could see things far away.他建了一个望远镜，通过它，他可以看见远处的东西。
③当先行词本身是that时，使用which。
例
The predicate is that which is said of the subject.
谓语是对主语的陈述。
④当关系词后面有插入语时。
例
Here is the ALD which,as I have told you,is a great help to you.这是《牛津高级学者字典》，正如我告诉你的那样，对你会有很大的帮助。
（3）在下列情况下，只许用关系代词who，而不使用that：
①先行词为those,one,ones,anyone,people等时。
例
Those who are from Qingdao come this way.
从青岛来的人，这边走。
Anyone who breaks the law should be punished.
无论是谁，犯了法，都应该受到惩罚。
③当先行词后有较长的后置定语时，或定语从句被分隔时。
例
A teacher will come tomorrow who will teach you German.
明天就要来一位老师，他将教你们德语。
③当先行词是用-body或-one构成的不定代词时，关系代词多 使用who。
例
Is there anybody else who should be invited?
还有没有要邀请的别人呢？
④当先行词是集合名词时，如果着眼于集体，使用 that／ which；如果着眼于个体，则使用 who。
例
Our team,which took the second place last year,played better this year.
我们队去年取得第二名，今年打的比去年好。
Our team,who are all under the age of twenty,will do well in the final match.
我们队的队员都不到20岁，将在决赛中，好好打。
（4）关系代词as和which的区别
①二者都可以引导非限制性定语从句，用来修饰或限制整个 主句的内容，有时可以互换使用。
例
He is a foreigner,as/which I know from his accent.
从他的口音我知道他是个外国人。
②定语从句放在句首时，只用as，不能使用which。
例
AS anybody can see,a computer can do almost everything people can.
正如人人所见，计算机几乎可以做人能做的一切事。
③当非限制性定语从句为否定句时，常使用which引导。
例
Mr Zhang usually criticizes Mary in public, which shedoesn't like at all.
张老师经常在公开场合批评玛丽，这是她根本不喜欢的。
④当非限制性定语从句的谓语是一个复合结构时，常使用which引导。
例
Little Bob always tells a lie,which his parents find strange.
小鲍勃总是说谎，这使他的父母感到很吃惊。
⑤当as在从句中作主语时，后面的谓语动词常常使用被动语态；如果从句中是主动语态，一般多使用which。
例
She has been late again,as was expected.
她又迟到了，这在意料之中。
Tom made great Progress in Chinese,whlch made us delighted.
汤姆的中文取得了很大的进步，这使我们很高兴。