D. All of the above
Ground level ozone is created when sunlight reacts with certain chemicals that come from sources of burning fossil fuels, such as factories or car exhaust. When particles in the air combine with ozone, they create smog. Smog is a type of air pollution that looks like smoky fog and makes it difficult to see. Additionally, Cities located in basins surrounded by mountains may have smog problems because the smog is trapped in the valley and cannot be carried away by wind
