What problems does mexico city have because of overpopulation?

Mexico City has a very troublesome pollution problem due to both the high population as well as the city's location within a valley region. The sheer number of people means there is a high output of pollutants and carbon emissions. The location in a valley means those emissions cannot easily escape the area and instead tend to "pool" and "sink" within the valley resulting in very thick and unhealthy smogs.

The correct option to this statement would be true

Iwould choose c or d