单项选择题 （）is a type of fog occurring close to the sea surface when the air is dry and cold-probably at least 9℃ below the sea surface temperature.

单项选择题 （）forms over land，most frequently during autumn and winter over low-lying land，especially if it is damp and marshy and in valleys on quiet nights with clear skies.

单项选择题 （） blow more or less constantly（except when monsoons prevail）throughout all seasons at a mean speed of around 14 knots and are generally strongest in the late winter.