B: becomes foggy or rainy because cool air holds less water vapor.
Explanation:
The maritime tropical air masses are warm and humid, while the air masses forming over the land tend to be dry, in some parts are cold and in some parts hot. When these two collide, the weather rapidly changes. If the maritime tropical air masses moves toward the colder ground surface, then the weather will become foggy or rainy.
The reason for this is that the water vapor in the maritime tropical air mass will start to condensate because of the lower temperatures, so precipitation will form. The precipitation is usually manifested through rainfall, while in the mornings it tends to be foggy.
