(1)that 既可以用于指人,也可以用于指物。在从句中作主语、宾语或表语。作主语时不可省略,作宾语可省略。例如:
Mary likes music that is quiet and gentle.
The coat (that) I put on the desk is blue.
我放在桌子上的那件外套是蓝色的。(that作宾语)
(2)which用于指物,在句中作主语、宾语或表语。作主语不可省略,作宾语可省略。例如:
The building which stands near the train station is a supermarket.
The film (which) we saw last night was wonderful.
(3)who, whom用于指人,who 用作主语,whom用作宾语。在口语中,有时可用who代替whom。who和whom作宾语时也可省略。例如:
The girl who often helps me with my English is from England.
经常在英语方面帮助我的那个女孩是英国人。(作主语)
Who is the teacher (whom) Li Ming is talking to?