Advection fog is primarily formed due to which of the following conditions?

Advection fog typically forms when warm, moist air moves over a colder surface, such as a cold body of water. This movement causes the air to cool down to its dew point temperature, leading to the condensation of moisture in the air and resulting in fog. The process primarily relies on the horizontal movement (or advection) of air masses, which is why the formation is named "advection fog."

In contrast, the other conditions described do not create the same environment conducive to the development of advection fog. For example, cooling due to the ground at night leads to radiational fog, while the warming of cold air by ground heat generally produces different types of fog. Lastly, warm air moving over warm water lacks the necessary temperature gradient to enable condensation, which does not lead to fog formation in the way that cold air over cold water does. Therefore, the conditions associated with cold air moving over a cold body of water best represent the formation of advection fog.