Environmental problems are becoming more and more serious all over the world.For example, cars have made the air unhealthy for people to breathe and poisonous gas is given off by factories. Trees on the hills have been cut down and waste water is being poured continuously into rivers.urthermore, wherever we go today, we can find rubbish carelessly disposed.Pollution is, in fact, threatening our existence.

　　全世界的环境问题变得越来越严重。例如汽车污染的空气影响了人们的呼吸，工厂释放污染的气体，山上的树木被砍伐，污水不断被排人河里。另外，无论我们走到哪里，到处可见随意丢弃的垃圾。事实上，污染正威胁我们的生存。