So if you're smart, you tend to be friends with smart people, and if you're young, you tend to be friends with young people, and this is well established for hundreds of years.
所以说，如果你很聪明，你倾向于和聪明的人交朋友。 如果你还年轻，你倾向于和年轻人交朋友。 这是数百年来 公认的理论。