Seeking the answer to the question of the twilight line in high school geography

When the height of the noon sun at H is 66°34 'and the area at G is 6 o'clock, then the faint line is
The answer is AC or TF
[My answer is either A B or D E, because G is now at 6 o'clock, and G is on the equator. Then G should be at sunrise at this time, and everything passing through it should be the morning line. At this time, H should be 18 o'clock, and everything passing by it should be in a blur. But the answer was the exact opposite.
Also, I want to ask what the sun's height is in this question. I think it should only be the solstice.

Answer 1

The twilight line was formed by the sun's rays passing through a point on the earth's surface. This line was called the twilight line. The closer the twilight line is to the equator, the smaller the angle of the sun's rays. Because the closer it is to the equator, the smaller the angle of the sun's altitude. The sun travels on the equator for about 12 hours, so the difference in longitude on the twilight line is also the smallest. On the contrary, the further away from the equator, the greater the sun's altitude angle, the longer the sun's rays travel on the equator, so the difference in longitude on the twilight line is greater.

In high school geography, the twilight line was often used to describe the change in the length of day and night and the change in the position of the sun. When the sun is on the equator, the sun's rays are vertical to the ground. The length of day and night is equal to the twilight line. When the sun rises or sets, the rays of the sun gradually tilt so that the twilight line gradually bends. In the northern hemisphere, when the sun is due north, the twilight line points due north. The closer it is to the equator, the straighter it is. In the southern hemisphere, when the sun is due south, the twilight line points due south. The closer it is to the equator, the straighter it is.

In addition, the twilight line was also used to describe the time zones and seasonal changes in different regions. By comparing the position and shape of the twilight line, one could determine the time zone and seasonal changes in different regions. For example, the area near the equator could be classified as a tropical time zone because the length of day and night was equal to the length of the twilight line. The areas near the polar circle could be divided into polar day or polar night time zones due to the small bending of the twilight line at the sun's elevation angle.