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

Multiple Choice

A research study of approximately 13,900 incoming freshmen in U.S. universities and colleges looked at the relationship between the amount of time a student spends drinking alcohol and the student's GPA, with a negative association observed between the two variables.
What is the explanatory variable in this study?

A) The 13,900 incoming freshmen
B) All American universities and colleges
C) The amount of time a student spends drinking alcohol
D) A student's GPA