Question

Why are air pollution levels higher in Mexico City than in other similarly densely populated cities?

because Mexico City is surrounded by mountains that trap polluted air


because Mexico City receives a large amount of precipitation each year


because Mexico City contains more cars and buses than other large cities


because Mexico City engages in more industrial activity than other large cities

Answer 1

because Mexico City is surrounded by mountains that trap polluted air

The basin-like topography (and frequent temperature inversions) prevents pollutants from dispersing, leading to buildup and smog. (High altitude and strong sunlight also worsen photochemical smog; heavy precipitation would reduce pollution.)