Professor Todd Decides to Test Her Hypothesis That Eating Chocolate

Professor Todd decides to test her hypothesis that eating chocolate prior to exams increases students' test scores.She randomly assigns students to two groups at the beginning of the semester.One group receives a bar of chocolate before each test,while the other group receives another type of candy.She compares their scores at the end of the year,and finds that the students who ate the chocolate scored an average of ten points higher on their exams.What is a fair conclusion that can be drawn from this experiment?

A) Eating chocolate causes students' test scores to increase.
B) Eating chocolate has no relationship to students' test scores.
C) Eating chocolate may increase students' test scores.
D) Eating chocolate makes students happy.