I know the girl who is under the tree.先行词 girl 关系代词 who
He is the man that I met yesterday 先行词 man 关系代词 that
The book which is on the desk is mine 先行词 book 关系代词 which
This is the watch which I bought last week 先行词watch 关系代词 which
造四个定语从句的句子、并告诉我、先行词是那个、关系代词是那个、