第11题: [单项选择]Questions 30 to 32 are based on the passage you have just heard. A. Power plants burn coal. B. Factories pour sewage. C. People bury trash underground. D. City population increases greatly. 参考答案:A 答案解析:[听力原文] 30-32 Clean air is important to good health. If the air contains impurities, they may