If warm moist air flows over a cold land surface which type of fog may form?

Correct answer: Fog formed by contact cooling

Correct answer: A. When warm, moist air moves across a colder land surface, heat passes from the air toward the surface. The lowest part of the moving air is cooled by contact with that surface. If its temperature falls to the dew point, water vapour condenses into many tiny droplets, producing fog. This is commonly described as contact cooling; when air is transported over a colder surface, it is also associated with advection fog. A is correct because it identifies the actual cooling process. B is wrong because dust may be a particle source but is not the named fog-forming process here. C is wrong because volcanic activity is not given and is unrelated to this ordinary cooling setup. D is not a standard meteorological category and combines unrelated terms. Memory cue: warm moist air plus a cold surface equals cooling to the dew point and possible contact or advection fog.