The picture shows the temperature change in a certain place in Zhejiang within 24 hours from May 29th to 30th. After reading the picture, I finished the question 18 ~ 19. At this time, this place was

The picture shows the temperature change in a certain place in Zhejiang within 24 hours from May 29th to 30th. After reading the picture, I finished the question 18 ~ 19. At this time, this place was subjected to () a. cold front B. A, the temperature in the picture has been falling, and the temperature difference is above 10 degrees, which should be a cold front crossing the border, so that's right;

B continuous precipitation occurs when the warm front crosses the border. After crossing the border, the temperature rose, the air pressure dropped and the weather turned fine. The temperature in the picture has been falling, and the temperature difference is above 10 degrees, which should be a cold front crossing the border, which does not meet the meaning of the question;

C, low pressure control rainy weather, low pressure when crossing the border. However, there is no change in air pressure in the picture, which does not conform to the meaning of the question;

D. Generally, under the control of high pressure, it is popular to flow downwards, and the temperature becomes higher, which makes it difficult to condense, resulting in less rainy weather. However, the air pressure in the picture has not changed, which does not meet the problem.

So choose: a.