最后，环境污染也是生活在大城市的一个重要挑战。由于越来越多的工厂，和大

Finally, the environmental pollution is a major challenge to live in the big city. As more and more of a growing number of factories, cars and big cities, they will produce gas pollution, urban air quality is getting worse. Due to the large population, many people littering also caused a deterioration of the urban environment

Finally, environmental pollution is also an important challenge in living in large cities. As more factories and more cars in big cities produce polluting gases, the air quality in cities is getting worse and worse. Because of the large population, many people litter ingen udy the urban environment.

Finally, environmental pollution is also an important challenge for living in big cities. As more and more factories, and more and more cars in big cities, they will produce pollution gases, and the air quality of cities is getting worse and worse. Because of the large population, many people throw rubbish at random, which also causes the deterioration of the urban environment