Summer in the northern hemisphere occurs in June-Sept, because a. the Earth is experiencing retrograde motion. b. the Sun's light hits that hemisphere less directly during that time of year. c. the Earth is farthest from the sun at this time of year. d. the Sun's light hits that hemisphere more directly during that time of year. e. the Earth moves more slowly around the Sun at this time of year. f. the Earth is closest to the Sun at this time of year.