Air is necessary for our existence of all living things. But now air is in the worst condition. So we should protect it. Firstly, we have to use electric cars and bicycles. If we ride bikes, we’ll protect our air and we’ll keep fit. I think riding bicycles is amazing kind of sport. Secondly, we should not cut down trees in our forests. Because trees produce oxygen and any living thing can’t live and breathe without it. Finally, we should use “clean” fuels, such as natural gas. When fuels burn, so many harmful substances emitted into the atmosphere, such as sulfur oxide and nitrogen oxide. Everything is in our hands! Just do it.