When answering this question, you can discuss the different sources of air pollution. Mobile vehicles, like cars, trucks, and buses, are definitely a major cause, especially in big cities, because they release exhaust fumes and harmful gases. However, you can also mention that there are other significant sources, such as factories, power plants, and even burning waste. It’s good to show a balanced view and maybe give an example from your own city or country.

回答这个问题时，你可以讨论空气污染的不同来源。移动交通工具，如汽车、卡车和公共汽车，尤其是在大城市中，绝对是一个主要原因，因为它们排放废气和有害气体。然而，你也可以提到还有其他重要的来源，比如工厂、电厂，甚至焚烧垃圾。展示一个平衡的观点是很好的，也可以举一个你所在城市或国家的例子。