题目

In American schools there is something called Home-coming Day. Many high schools and colleges with a football team have a home-coming game. This can be the most important event of the year except graduation (毕业) day. Students plan Home-coming Day for many weeks in advance. Several days before Home-coming ,students start to decorate (装饰)the school. There are signs to wish luck to the team, and many other signs to welcome all the graduates. Many people still come to Home-coming twenty or thirty years after their graduation. The members of school clubs build booths (摊位) and sell为响应“低碳生活”的号召，小明每天骑自行车上学．他看到路边的小树向后“飞过”，是以    为参照物的．如果他在平直的公路上骑过3km用了10min，则他骑车的速度为    km/h，合    m/s．