As shown in the figure, the air pressure distribution in a certain area at a certain moment (unit: hectopascals). Look at the picture and answer questions 3-4. If the weather system moves eastward,

A. If the weather system moves due east and the air pressure in Beijing becomes 1020 hectopascals after 48 hours, then during this time, Beijing.

The wind direction changes from northwest to northeast, so it is correct;

B. If the weather system moves due east, the air pressure in Beijing will become 1020 hectopascals after 48 hours. During this time, the isobar in Beijing is dense, and the wind speed changes from slow to fast, which does not meet the question.

C. If the weather system in the picture moves due east, the air pressure in Beijing will become 1020 hectopascals after 48 hours, and the weather in Beijing is mainly sunny during this period, which does not meet the question;

D. If the weather system moves due east, the air pressure in Beijing will become 1020 hectopascals after 48 hours. During this time, the air pressure in Beijing will gradually increase, which does not meet the question.

So choose: a.