Read the chart "Weather System Diagram at 7 o'clock and 14 o'clock on a certain day" and complete questions 3-4. The weather process experienced by ② in the picture is () A. The wind direction changes from southerly to southerly.

A, the specific point on the isobar diagram is that the wind direction is from high pressure to low pressure, and the northern hemisphere deflects to the right. At 7 o'clock, the wind is southerly, and at 14, the wind is westerly, which is correct;

B. At 7 o'clock, ② the low pressure is greater than 10 10HPA and less than1015hpa; At 14, ② atmospheric pressure is greater than 1005 hectopascals and less than 10 100 hectopascals. Atmospheric pressure has been decreasing, so it doesn't meet the problem.

C, at 7 o'clock, the ground is behind the warm front, controlled by a single warm air mass, and the weather is fine; 14, ② The ground is behind the cold front, and it is rainy. In this process, the temperature has not been falling, so it does not meet the question.

D, at 7 o'clock, the ground is behind the warm front, controlled by a single warm air mass, and the weather is fine; 14, ② The ground is behind the cold front with precipitation. The weather changed from sunny to rainy, which did not meet the problem.

So choose: a.