【答案解析】[参考范文] Smoking is a widespread bad habit. Many people, young and old, smoke. Nowadays even middle school students an~ developing this bad habit. Firstly, smoking is bad because it is harmful not only to the smoker's health, but also to public health. Smoking is one of the major causes of lung cancer, pneumonia (肺炎) , and heart attack. Secondly, smoking also pollutes the environment. Many people have the bad habit of carelessly throwing cigarette ends anywhere. Finally, due to the smoker's carelessness, cigarette ends may cause fire, which may destroy buildings, properties, forests, and even lives. Therefore, smoking should be banned in public places.