Which of the following are known to have top-level pollution?

One disadvantage of living in a city is the crowded streets. Due to the large number of vehicles, especially during rush hour when people are travelling to and from work, traffic in the city is a problem. Pollution levels in the city are exceptionally high. Because of poor waste management, industrialization causes environmental damage. Another negative feature of living in a city is the sewage system. The same sewage system is used by many upper-class residents, and if it is not properly maintained, it could become clogged. Overcrowding is another issue in the city. It is difficult to stroll since it is uncomfortable because you may surely run into other individuals on the streets. As a result, choice D is the correct response.