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 every week. At the end of this semester, their GPA is recorded as well. The resulting information is categorized per students into two variables: physical activity and semester's GPA. The primary interest of the research is to understand if physical activity promotes better academic performance.

1. What type of study is this?

A. Observational study

B. Randomized experiment

C. Matched pairs study.

D. Repeated measures study

E. None of the above

2. Which of following principles are used in this study?

A. Randomization

B.Control

C. Replication

D. Blinding

E. None of the above

3. Which variables is the explanatory variable in this study?

A. The diary

B. Physical activity

C. GPA

D. Academic performance

E. None of the above