How does fog typically form?

Fog typically forms through the process of cooling air to its dew point, which is the temperature at which the air becomes saturated with moisture. When warm, moist air cools, it can no longer hold all of its water vapor, leading to condensation and the formation of tiny water droplets that create fog.

This phenomenon usually occurs during the night or early morning when the ground loses heat, causing the temperature of the air near the surface to drop. As the air cools down to the dew point, it condenses into fog.

The other options involve processes that do not lead to fog formation. Increasing temperature and reducing humidity would actually make the air drier and less likely to form fog. Adding pollutants can affect visibility but does not directly cause fog. Raising the air temperature would also prevent the air from reaching its dew point and therefore prevent fog formation.