The boy _ is standing under the tree is my friend Tom.He lives in a house _ stands on a hill.That little girl_ Tom often helps is his sister Mary.The bird _ is singing in the cage is Toms too.Bob is his dog _ Tom and Mary often play with.The dog is great.Yesterday he caught a thief _running away.Exercise 2:用用who/whom/which/that填空填空who/thatwhich/thatwho/whom/thatwhich/thatwhich/thatwho/that1.引导定语从句。引导定语从句。2.代替先行词。代替先行词。3.在定语从句中担当一个成分。在定语从句中担当一个成分。关系词的三个作用关系词的三个作用:确定关系代词的步骤确定关系代词的步骤1.先找先行词，先找先行词，
