What type of research method assesses changes in behavior in one group of subjects at more than one point in time?

Can someone read this article and tell me the 1) key ideas and 2) one key quote (copy and paste the link the article is not to long at all)from

When comparing the northern and southern hemisphere, why are the peak maximum and minimum values of insolation at different times of the year? specifically, why is the peak max of incoming solar radiation in june for the northern hemisphere, but in december for the southern hemisphere? pick the best, most complete answer. because of variations in the incident angle of solar radiation, due to the tilt of earth's axis, the northern hemisphere receives more direct solar radiation in june while the southern hemisphere receives less direct solar radiation. the reverse is true in december. because of earth's tilt, as the earth progresses in its revolution around the sun, the northern hemisphere is relatively closer to the sun in june while the southern hemisphere is relatively farther from the sun. the reverse is true in december. because of earth's elliptical orbit, the northern hemisphere is relatively closer to the sun in june/july while the southern hemisphere is relatively farther from the sun. the reverse is true in december. because of variations in the incident angle of solar radiation and the length of day, due to the tilt of earth's axis, the northern hemisphere receives more direct solar radiation and has longer daylight hours in june while the southern hemisphere receives less direct solar radiation and shorter daylight hours. the reverse is true in december.

What was the focus of debate about the war at the second