Why are most polluted cities in the world located in developing nations

The reason why the most polluted cities in the world are in the developing countries are the bad planning of where the industry should be located, and not taking care of the environment but instead only focusing on making some profit. In the developing countries, the industry is often located inside the cities, and parts of the cities have been built around them, with the purpose of the workers to be closer to the place they work, thus the companies to avoid spending money on transporting the people, and to have the market right next to them. Also, in this countries, the industry still uses strictly fossil fuels, especially coal, and there's no filters installed to reduce the pollution. This leads to enormous pollution in the cities, with lot of toxic gasses being released inside them, and often stopping the proper movement of the air masses, resulting in the polluters to stay above and in the city for longer periods of time. We can see this in India, Pakistan, Macedonia, China.

d is the answer. leo should include the source.