There are two mice. They are called Bill and Paul. They are good friends. One mouse lives in the country; the other mouse lives in the city. On a sunny day they meet in the street. Paul: Hi, Bill! Have a look at my house in the country. I'm sure you can enjoy yourself. Bill: I'd love to. But I hear that the food is not delicious, and your house is not good. Is it so? Paul: No, that's not true. Go and see! Then Bill goes to the countryside with Paul. Bill: Why do you live in a hole in the field? You should come and live in the city. You would live in a nice house made of stone. You would have better food to eat. You must come and see me at my house in the city. Paul: Thanks! Maybe you are right. I'll visit your house one day.  _ days later Paul goes to Bill's house in the city. The house is big and beautiful. They are sitting in the sitting-room, having a big dinner comfortably. Suddenly, there a great noise. Bill: Run! Run! The cat is coming! Paul: Oh, no! It's terrible! Both the house and the food are nice, but I do not like living in the city. I enjoy living in my hole in the field, for it is nice to be poor but happy than to be rich but afraid. What the relationship between Bill and Paul?
They are friends. They are relatives. They are brothers. They are neighbors.