1.who指人，在從句中做主語
　　(1)The boys who are playing football are from Class One.
　　(2)Yesterday I helped an old man who lost his way.
　　2. whom指人，在定語從句中充當(dāng)賓語，常可省略。
　　(1) Mr. Liu is the person (whom) you talked about.
　　注意：關(guān)系代詞whom在口語和非正式語體中常用who代替，可省略。
　　(3) The man who/whom you met just now is my friend.
　　3. which指物，在定語從句中做主語或者賓語，做賓語時(shí)可省略
　　(1) Football is a game which is liked by most boys. ( which 在句子中做主語)
　　(2) This is the pen (which) he bought yesterday. ( which 在句子中做賓語)
　　4. that指人時(shí)，相當(dāng)于who或者whom;指物時(shí)，相當(dāng)于which。
　　在賓語從句中做主語或者賓語，做賓語時(shí)可省略。
　　(5) The people that/who come to visit the city are all here. (在句子中做主語)
　　(6) Where is the man that/whom I saw this morning? (在句子中做賓語)
　　5. whose通常指人，也可指物，在定語從句中做定語
　　(1) He has a friend whose father is a doctor.
　　(2) I lived in a house whose roof has fallen in.
　　whose指物時(shí)，常用以下結(jié)構(gòu)來代替
　　(3)The classroom whose door is broken will soon be repaired.
　　=The classroom the door of which is broken will soon be repaired.
　　(5)Do you like the book whose color is yellow?
　　=Do you like the book the color of which is yellow?