1 1 US weather

Cold wave is the main disastrous weather affecting China in winter, which refers to a large-scale strong cold air activity. Specifically, the temperature drop in the middle and lower reaches of the Yangtze River and its north area exceeded 10℃ within 48 hours, and the lowest temperature was below 4℃. It can be regarded as a cold wave, accompanied by 5-7 winds on land and 6-8 winds at sea. The south of the cold wave caused a sharp drop in temperature, frost and strong wind in the passing area.

Therefore, choose: d.