是否可以省略：which 指物，在定语从句中做主语或宾语，做宾语时常可省略。
用法不同：which 表明先行词是物（也指事）在限定性定语从句中=that,在非限定性定语从句中只能which，不能用who。
代指对象不同：which一般指代事物、动物，或者指代婴儿、小孩；who指代人或者拟人化的动物。如:
The book which I bought is very cheap.我买的书非常便宜。
I know the man who stole Mary's wallet.我认识偷玛丽钱包的人。
1、who 表明先行词是人（一般在从句中充当主语）
The boy who plays computer well is waitting for you.
2、which 表明先行词是物（也指事）在限定性定语从句中=that,在非限定性定语从句中只能which
This is the hotel which/that you will stay in.
Tom is late for class,which makes his mum very angry.
Beijing,which ia the capital of China,is a beautiful city.
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