High school geography, about the length of day and night, ask for a detailed explanation.

Comparing the sunrise time difference between the two places, if the two places are on the same meridian, the curve of the time difference statistical chart should be a complete approximate sine curve within one year (the blue line above). Among them, the daily business trip at D, M and d' is theoretically 0, and the solar terms are divided into two parts. Point C is the summer solstice or the winter solstice. The daily business trip between the two places is plus or minus six months.

However, the curve does not reflect the above characteristics. When we translate ad into a' d', we get a complete curve, which only shows that A and B are not on the same longitude.

When a complete curve is obtained through translation, it actually pulls both parties to a meridian (see the coordinates on the right). According to the above description, D, M and D' are located on the bisector (the sunrise difference between them is -0.6 hours, but in fact the longitude difference must be 9, and A is located in the west of B). C is the second day to the third day.

So option d is correct.