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.

在回答這個問題時，你可以討論不同的空氣污染來源。移動的交通工具，如汽車、卡車和巴士，無疑是主要原因，尤其是在大城市，因為它們排放廢氣和有害氣體。然而，你也可以提到其他重要來源，例如工廠、發電廠，甚至焚燒廢棄物。展示一個平衡的觀點是好的，或許還可以舉自己所在城市或國家的例子。