Auniversity 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