I met someone who said he knew you.
关系代词 who 代表 someone，又引导从句修饰它，同时又在从句中担任主语。关系代词 who, whom, whose, that和 which可以用来引导定语从句，这类代词都起着三重作用，一是代表前面的名词，二是把从句和它所修饰的词连接起来，三是在从句里也担任一个成分。who 和 whom 都代表人，who 在从句中作主语，whom在从句中作宾语或介词宾语。whose在从句中可以作定语。that可以代表人或物，which 只能代表物在从句中可充当主语、宾语或介词宾语等。
(1) The noise that she made woke everybody up.
语法分析：that 代表 noise，又引导从句修饰它，在从句中担任 made 的宾语。
(2) She saw something in the paper which might interest you.
语法分析：which 代表 something, 又引导从句修饰它，在从句中担任主语。
(3) The girl with whom I was travlling didn't speak English.
(4) I saw a film whose name I have forgotten.
(5) Who's the man (that) you were talking to?
(6) The situation in which she found herself was very difficult.
1. The man _____ robbed her has been arrested.
2. The man _____ I saw told me to come back tomorrow.
3. I know a girl _____ mother is an acrobat.
4. He _____ would eat the fruit must climb the tree.
5. The dog _____ was lost has been found.
6. She invited us to dinner, ______ was very kind of her.
7. My dog, ______ temper is very uncertain, often bites judges at dog show.
8. The man from ______ I brought it told me to read me instructions.
1. who 2. whom 3. whose 4. that 5. which 6. which 7. whose 8. whom