1、先行词为one, ones, anyone, those指代人时。如: The person I want to learn from is one who studies hard and works well.我最羡慕的是学习勤奋,工作出色的人。
2、在There be结构中,修饰主语的定语从句宜用 who关系代词指代人。例如: There’s a gentleman who wants to see you.有位先生想见你。
3、当先行词有较长的后置定语时。例如: I met a foreigner in the park yesterday afternoon who could speak Chinese very well.昨天下午我在公园里遇到一位中文讲得非常好的外国人。
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是that, 另一个宜用who以避免重复。The student that was praised at yesterday’s meeting is the monitor who is very modest and works very hard.受到校长表扬的学生是位谦虚好学的班长。
注意:当关系代词前面有介词时,只能用whom。例如: The person to whom this letter was addressed died three years ago.这封信的收信人三年前就去世了。