世界上绝大多数动植物都能在我国找到适合生长的地方，主要因为（   ） 

用代入法解方程组有以下过程，其中错误的一步是（　　）

（1）由①得x=$\frac{8-3y}{2}$③；

（2）把③代入②得3×$\frac{8-3y}{2}$﹣5y=5；

（3）去分母得24﹣9y﹣10y=5；

（4）解之得y=1，再由③得x=2.5．

    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.”