3. Among the following groups of solar terms, the longest days in Beijing are A, Qingming, Beijing-Zhejiang B, beginning of winter, beginning of spring C, Xiaoxue, Xiaohan D, rain,

In the following groups of solar terms, the sky in Beijing is closest to B, beginning of winter and beginning of spring.

A, Qingming, Jingzhe B, beginning of winter, beginning of spring C, Xiaoxue, Xiaohan D, Rain and Summer.

There are direct sunlight twice a year between the Tropic of Cancer. For the same place, the day and night of direct sunlight at the same latitude are the same. Therefore, the solar terms with the same distance from summer solstice or winter solstice are closest to the latitude of direct sunlight, and the length of day and night is also the closest. Beginning of winter and beginning of spring are three squares apart from the winter solstice, so the sky in Beijing is closest to B, beginning of winter and beginning of spring.