A study is designed to determine whether or not taking four years of math in high school helps students' chances of acceptance at NC State.

• At a particular high school, 300 students were not permitted to take a fourth year of math, and 300 students were required to take a fourth year of math.
• In comparing the acceptance rates of the 600 students at NC State, it is noted that the average entrance rate for those who took a fourth year of math is higher than those who took three years of math.
• Based on this experiment, guidance counselors began recommending a fourth year of math for college-bound students.

Which of the following is not true?

A. A more meaningful study would be to do an observational study on an SRS of students who have already signed up for a third of fourth year of math.

B. This study proves that taking four years of math in high school gives students a higher acceptance rate into NC State.

C. No conclusion can be made about the relationship between taking four years of math and acceptance rates.

D. This is an experiment, not an observational study.