已知定义域为R的函数f（x）=$\frac{-2^x+b}{2^{x+1}+a}$是奇函数．

（1）求a，b的值；

（2）解不等式f（x）＜$\frac{1}{4}$；

（3）求f（x）的值域．

    People in the UK spend their free time in different ways. They usually use it to relax. They spend a lot of their free time at home. The most popular activity is watching TV. People in the UK watch TV for about 25 hours a week. They often record (录制) programs so they can watch them later. Reading is also a popular way of spending free time. People in the UK spend a lot of time reading newspapers and magazines. Many people in the UK have pets. They like playing with their pets in their free time.

    In summer， gardening (园艺) is popular. And families often have a “day out” on the weekend. They often go to a festival or see a show. Young people like to go to clubs， and people of all ages like to go to the cinema.

    In winter， “do-it-yourself” is popular. People often spend their free time repairing (修理) houses.

    Some free time activities are with friends. Asking friends for a drink or a meal at home is the most usual one. Sometimes people and their friends have dinner in a restaurant.

    On the weekend， people in the UK like to spend their free time doing sports. The popular kinds of sports are soccer， horse racing， swimming， tennis， skating， climbing and hill walking.

根据材料内容选择最佳答案。

天上的月亮看见人类总是乱丢垃圾,肆意砍伐树木,还把污染过的水倒进河里,心里会怎么想呢?它会怎么样来劝人类呢?请你以“月亮的劝说”为题目写一篇习作,不少于350字。