第20题:[简答题]假设你是一个农村学生，进城看到河水被严重污染，请写一篇议论污染的日记。内容包括以下几点：
1．河水颜色发黑，并发出臭味。
2．水里没有鱼，也没人游泳。
3．污染原因是附近的工厂往河里排放工业废水。
4．大家应保护环境，减少污染。
注意：
1．要符合日记的格式。
2．词数为l00左右。
参考答案:One possible version :
September 16,2012, Sunday Cloudy
I went to the small city far away from villages to buy some books this morning. What I saw there sur-prised me very much. There is a river in the city. The water in it is dark and smells terrible. It is polluted with eh 1 waste from factories. There are many small factories along the river. Their waste is poured directly into the river. The wont one is the paper factor. It pours waste water into the river day and night. Fish can't live in such a polluted river and neither can people swim in it. I wonder why people don' t care about our environment. We should do something to reduce pollution.
第25题: [单项选择]下述不属于数据库维护工作的是______。 A. 使用数据定义语言建立多个表、构建数据库总体框架 B. 根据备份计划周期性的备份数据库 C. 检测数据库的空间使用情况 D. 调整数据库参数，进行性能优化 参考答案:A 答案解析:[解析] 数据库维护工作主要包括：数据库的转储和恢复，数据库安全性、完整性控制，数据库性能的检测与改善以及数据库的重组和重构，所以本题的答案为A。
