The correct answer is D) thunderstorms, hail, and then rapid clearing. A cold front moving in from the northwest can produce a rapid change in weather conditions, often including thunderstorms, hail, and then quick clearing as the front passes. This is due to the sudden shift in air masses as the cooler, drier air of the cold front replaces the warmer, more humid air ahead of it. The thunderstorms and hail are caused by the instability and lift associated with the frontal passage, while the rapid clearing occurs once the frontal system has moved through the area. The other options are incorrect because they do not fully capture the dynamic nature of the weather changes that can occur with a cold front. Option A describes a more gradual increase in cloud cover, option B focuses on low clouds without the thunderstorm activity, and option C suggests a prolonged period of wet weather, which may not always be the case with a cold front passage.