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。