Nowadays, with the living standards improving fast, masses of people own cars, which certainly benefit them a lot. But more and more cars will give out poisonous gases and cause air pollution, which does great harm to the environment.现在，随着生活水平的快速提高，许多人拥有汽车，这肯定对他们很有益处。但是，越来越多的车会放出有毒的气体并造成空气污染，对环境极为有害。Therefore, human beings are...
