Use the Following Information for Questions

Multiple Choice

Use the following information for questions:
Fifty university students are randomly chosen from the college campus. Their physical fitness routines and academic performance will be assessed. They are asked to maintain a diary over a semester to record their physical activity (i.e. work-outs) every week. At the end of this semester their GPA is recorded as well. The resulting information is categorized per student into two variables: physical activity (recorded as "above average", "average", or "below average") and that semester's GPA. The primary interest of the research project is to understand if physical activity promotes better academic performance.
-Which variable is the explanatory variable in this study?

A) The diary
B) Physical activity
C) GPA
D) Academic performance