The correct answer is B) A line of cumulonimbus clouds. The passage of a cold front in the Northern Hemisphere is typically accompanied by the development of a line of cumulonimbus (thunderstorm) clouds. As the cold front moves through, the cooler air mass behind the front causes rapid upward motion of warm, moist air, leading to the formation of these towering, vertically-developed clouds associated with thunderstorms. The other answer choices are incorrect: A) is not correct as barometric pressure generally rises behind a cold front, not drops; C) is incorrect as the wind shift is from southwest to northwest, not northeast to southwest; and D) is incorrect as precipitation may be present but not necessarily steady or increasing in intensity through the passage of the cold front.