The correct answer is A. If you live in the Midwestern United States or Canada and you experience several days of winter temperatures below 20°C with clear weather, you are undoubtedly experiencing a Continental Polar air mass.
Explanation:
Continental polar masses are air masses that are cold and dry due to their region of origin. Polar continental air masses that affect North America form in further inland Canada.
Both the continental polar air masses and the Arctic air masses are highly stable; the temperature gradient in the lower layers is much lower than the adiabatic one, and stratiform clouds are predominant.
