（213? A model of Tongan District) The Fujian Meteorological Observatory publishes the weather forecast of the whole province every day, as shown in the figure, which lists the temperature conditions of two cities on April 22, 213.

Answer: A city is Nanping, and B city is Xiamen. There are many sand stones in Nanping, and the specific heat capacity of sand stones is small. Under the same conditions, the temperature of sand stones changes greatly, so the daily temperature difference in Nanping changes greatly. In Xiamen, on the seashore, the specific heat capacity of water is relatively large. Under the same conditions, the same heat is absorbed (or released), and the temperature of water changes little, so the daily temperature difference changes little.