that which who whom 请问这些复合句的引导词有什么区别 什么时候可以省略 什么时候不可以 为什么？

Question

如题所述

Answer 1

which前面的先行词是物，who whom前面的先行词是人，who 在从句中作主语，whom做宾语或介词宾语；that 前面的先行词既可以是物也可以是人。that which who 在从句中作主语时不能省，做宾语时可以省。The man who robbed her has been arrested.抢她东西的人被捕了。
The man whom I saw told me to wait, 我见到的那个人让我等一会。同时这里的whom也可以省略，也可以用that代替。
The dog which/that was lost has been found.丢失的狗找着了。这里which/that作主语不可省。
The car （which/that） I hired broke down,我租的汽车坏了。that which可省。