You were asked to participate in an experiment to test the effectiveness of review sessions on exam grades. As a research methods student, you concluded that you had been assigned to the control group because you simply took the scheduled exams. Since you did not want the students in the experimental group to get higher grades than you did on the exams, you organized a review session with other control group subjects. This illustrates:

A. demoralization
B. maturation
C. the testing effect
D. compensation
E. compensatory rivalry