The correct answer is D) advection fog. Advection fog is the most common type of fog encountered at sea. It forms when warm, moist air moves over a cooler surface, such as the ocean. As the warm air cools, the moisture condenses and forms a dense fog layer near the surface. This is the primary mechanism for fog formation in maritime environments. The other options are less relevant for maritime conditions. Radiation fog forms overnight on land due to radiative cooling, conduction fog forms when warm air moves over a cold surface, and frontal fog is associated with the boundary between two different air masses - these types of fog are more common in coastal or inland areas rather than the open ocean.