In which situation does evaporation fog typically occur?

Evaporation fog, often referred to as steam fog, typically occurs when cold air moves over warmer water. This situation creates a temperature difference that facilitates the evaporation of water from the surface. As the warm, moist air rises into the cooler air, it cools quickly and condenses, leading to the formation of fog. This process is particularly evident in conditions such as autumn when cold air masses move over relatively warm lakes or rivers, resulting in visible fog as the moisture condenses.

In contrast, other scenarios presented do not generally lead to evaporation fog. For instance, warm air over cold land might create different types of fog associated with temperature inversions, while cool air rising over a mountain is more related to orographic lift and cloud formation rather than fog. Lastly, still air in a humid environment could lead to other forms of fog, but it would not specifically indicate evaporation fog as the primary mechanism involves temperature differences caused by warmer surfaces.