生物进化过程中最直接可靠的证据是（    ）

    Young people and older people don't always agree. They sometimes have different ideas about living, working and playing. But in one special program in New York State, adults and teenagers live together in a friendly way.

    Each summer 200 teenagers and 50 adults live together for eight weeks as members of a special work group. Everyone works several hours each day. They do so not just to keep busy but to find meaning and enjoyment in work. Some teenagers work in the woods or on the farms near the village. Some learn to make things like tables and chairs and build houses. The adults teach them these skills.

    There are several free hours each day. Weekends are free, too. During the free hours some of the teenagers learn photo taking or painting. Others sit around and talk or sing. Each teenager chooses his own way to spend his free time.

    When people live together, rules are necessary. In this program the teenagers and the adults make the rules together. If someone breaks a rule, the problem goes before the whole group. They talk about it and ask, “Why did it happen? What should we do about it?”

    One of the teenagers say about his experience, “You stop thinking only about yourself, you learn to think about the group.”