those当先行词时，指人时，常用关系代词who。例句:Those who are selfish never think about others.

That(指物)和those(指人或物)可做定语从句的先行词，this和these不可做先行词，those做定语从句先行词时，当其指物关系词用that/which等，当其指人时，关系词用who等，具体示例如下：

He admired those who looked beautiful. 他很喜欢那些看上去很美的人。（指人）

He admired those which looked beautiful. 他很喜欢那些看上去很美的东西。（指物）

(错)He admired that who danced well.（that不能指人）

(对)He admired those who danced well.他赞赏跳舞好的人。（those可指人）