The correct answer is A. Smoke and Fog.
Smog is a mixture of smoke and fog. It is a type of air pollution that is caused by the burning of fossil fuels, such as coal, oil, and gasoline. Smog can be harmful to human health, as it can cause respiratory problems, heart disease, and cancer.
Option B is incorrect because snow is not a type of pollution. Snow is a form of precipitation that occurs when water vapor in the atmosphere condenses and freezes.
Option C is incorrect because dust is not a type of pollution. Dust is a fine powder that is made up of tiny particles of rock, soil, or other materials.
Option D is incorrect because sulfur dioxide is not a type of fog. Sulfur dioxide is a gas that is released into the atmosphere when fossil fuels are burned. It can cause acid rain and other environmental problems.