A Research Survey of Approximately 13,900 Incoming Freshmen in U

A research survey of approximately 13,900 incoming freshmen in U.S. universities and colleges found that the amount of time a student spends drinking alcohol is a strong predictor of that student's GPA, and that there is a negative association between the two characteristics. Which of the following statements about these results is true?

A) We can conclude that drinking alcohol causes students to have a lower GPA)
B) We can conclude that a low GPA causes students to drink more.
C) We cannot conclude there is a causal link between drinking alcohol and GPA because the study did not include all incoming freshmen in the United States.
D) We cannot conclude there is a causal link between drinking alcohol and GPA because the data are simply observations, and association does not imply causation.