用定语从句合并句子
①I live next door to a couple. Their children often make a lot of noise. 
__I live next door to a couple whose children often make a lot of noise. __
②The man is from Peking University. I talked about the man at the meeting. 
__The man (who/whom/that) I talked about at the meeting is from Peking University. __
③The boy is sitting on the chair. The boy is my brother. 
__The boy who/that is sitting on the chair is my brother. __
④The city is near the sea. The city is very beautiful. 
__The city which/that is near the sea is very beautiful. __