Why do people get headaches in a crowded， stuffy room？ Because they are breathing bad air. People who breathe bad air for a long time can get really sick. They may even get lung cancer and die. People need fresh air. Fresh air cleans the blood. For our health's sake， we should all， there- fore， do our part to fight against air pollution.
空气污染
为什么人们在又挤又闷的房间中会头疼呢？因为他们呼吸着恶劣的空气。凡是长时间呼吸恶劣空气的人可能会生重病。他们甚至可能得肺癌死去。人们需要新鲜空气。新鲜空气能净化血液。为了健康起见，我们每个人都应该尽一己之力为反对空气污染而努力。