“外甥是先皇帝舅宿亲，又蒙降金城公主，遂和同为一家。天下百姓，普皆安乐。”这段话反映了中国古代哪两个民族之间的友好关系（   ）

根据对话的情景，从方框中选择适当的句子填在画线处，使对话完整通顺。其中有两项是多余的。
A: Hi, Zhou Yanhong. ____ 
B: I'm reading a book.
A: Oh, do you like reading?
B: Yes, very much. _____ 
A: I like playing the piano.
B: Good. By the way,____ 
A: It's easy and interesting. I like it a lot.
B: But I think it's difficult and boring. ____ I like Chinese best.
A: ____ 
B:Because I think it's useful (有用的) and interesting.