1. At which time of day is the heat flow entering Earth's atmosphere re (Hn) highest? (H_(n)) A. sunrise B. midday C. sunset D. midnight

The correct answer is B. midday.The heat flow entering Earth's atmosphere, also known as the net incoming heat flux (Hn), is highest at midday. This is because the Earth's surface receives the most direct sunlight at this time, resulting in the highest amount of solar radiation being absorbed by the Earth's atmosphere.At sunrise and sunset, the angle of the sun's rays is lower, which means the solar radiation is less direct and the heat flow entering the atmosphere is lower. At midnight, the sun is not visible, so there is no incoming solar radiation, and the heat flow is at its lowest.Therefore, the heat flow entering Earth's atmosphere is highest at midday.