求翻译：交通运输：汽车、火车、飞机、轮船是当代的主要运输工具，它们烧煤或石油产生的废气也是重要的污染物。特别是城市中的汽车，量大而集中，排放的污染物能直接侵袭人的呼吸器官，对城市的空气污染很严重，成为大城市空气的主要污染源之一。汽车排放的废气主要有一氧化碳、二氧化硫、氮氧化物和碳氢化合物等，前三种物质危害性很大。是什么意思？

Transportation: cars, trains, planes, ships of the principal means of transport, they are burning coal or oil emissions from pollutants is also important. Car, especially in cities, large and concentrated, pollutants emitted directly attacks the human respiratory organs, the city's air pollution is

Transportation: car, train, aircraft, ships, one of the principal means of transport they burn coal or oil exhaust pollutants are also important. The automobile industry, particularly in the cities of the large, concentrated, and emissions of pollutants can be direct attacks on the city's air pollut

Transportation: The automobile, the train, the airplane, the steamboat are the contemporary main transport means, their bunker coal or the petroleum produce the waste gas also is the important pollutant.In the city automobile, the quantity is specially big and is centralized, the emissions pollutant

Transportation: cars, trains, planes, ships were contemporary of the main means of transport, they generated by burning coal or petroleum pollutants from the waste gas are also important. Especially in the city car, large, centralized, emissions from direct invasion of respiratory organs, urban air