When I Look at the Number of Hours a Student

Multiple Choice

When I look at the number of hours a student sleeps on an average night and the student's overall GPA, I find that the data form an inverted (upside down) U. Students who get too little sleep or too much sleep do poorly whereas those who get about 7-8 hours do well. What kind of correlation should I see?

A) both a positive and a negative correlation
B) a zero correlation because it is a curvilinear relationship
C) a positive correlation because the data start off low and then get high
D) a negative correlation because the data end on a low point