A university study examined the relationship between amount of sleep and school performance in college-age students. The Venn diagram represents the students who participated in the study. If A represents the students who slept more than 7 hours per night, and B represents the students who improved in school performance, what group of students does region C represent? A. students who slept more than 7 hours per night and did not improve in school B. students who slept more than 7 hours per night and did improve in school C. students who slept for exactly 7 hours and performed at the mean level for school performance D. students that slept for exactly 7 hours and did not improve in school