补全对话
Bob: Hi, Bill! I’ve heard you are a football fan, aren’t you?
Bill: Yes.
Bob: (1) ____ 
Bill: Well, when I watch a football game, I feel excited. (2)____ 
Bob: Just a little bit. I’m not good at playing football. (3)____ 
Bill: Oh, I see. Do you have any favourite football stars?
Bob: (4)____ 
Bill: Oh, I like him, too.
Bob: (5) ____ 
Bill: Not much. I’m going to join a football club so that I can play football more.
Bob: That’s a good idea

欧洲人形成以乳畜产品为主要食物的饮食习惯是因为：欧洲（  ）