a) 关系代词who的用法
i. who 的前行词必须是人，在从句中可以担任主语，往往也可以代替在从句中担任宾
语的whom,但是它前边不能有介词，如果带了介词就必须用宾格的whom:
（介词+whom）
This is the teacher who teaches us mathematics.
She is the girl who (whom) I met at the party. （可以替代）
She is the girl whom (who) I went there with. （可以替代）
She is the girl with whom I went there. （不可替代）
ii. who，that在很多情况下可以通用，但是有些情况只能用who:
1. 先行词是one, ones, anyone的时候宜用who.
One who has nothing to fear for oneself dares to tell the truth.
The ones who flatter me don’t please me.
Don’t tell anyone about the news who oughtn’t to know it.
Anyone who fails to finish the task given should be criticized.
2. 先行词为those的时候，宜用who为关系代词
Those who were not fit for their work could not see the beautiful clothes
made of the magic cloth.
Those who want to go to the Great Wall sign up here.
3. 当先行词有比较长的后置定语的时候
I met a foreigner in the street yesterday who could asked me questions in
Chinese.
4. 一个句子中带有两个定语从句，其中一个定语从句的关系代词为that,另一个则用
who.
The boy that you met last night is the group leader who studies very hard.
5. 在there be 开头的句子中
There is an old man who wants to see you.
There are many young men who are against him.
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