[填空题]Energy use and air pollution have been synonymous in China for decades, especially in urban areas. (66) Fifteen or 20 years ago in China’s northern cities, such as Shenyang, air pollution was characterized by decreased visibility caused by high levels of particulates and sulfur dioxide (SO₂). Although conditions have improved in modern cities, such as Beijing and Shanghai, China still has three of the ten most polluted cities in the world and hundreds of cities that are not in compliance with the World Health Organization (WHO) air quality guidelines.
(67) More than 120 cities have populations of more than one million, and by the end of the twenty-first century, 10 to 20 cities will have populations of more than 10 million. Rapid urbanization will challenge governments at all levels, not only to provide basic services to growing urban populations, but also to modernize, to continue to develop economically, and to address environmental concerns, particular