Students who received tutoring to pass a test scored significantly higher than those who did not. This year, substantially more students achieved high scores on the test. This does not mean that the tutoring on offer to students has gotten better. During this academic year, more new schools that offer tutoring opened. Therefore, it is likely that more students took the test this year than last year. Which of the following would be the most useful to know to evaluate the argument above?
A. Whether students taking other exams this year scored better than those who took the same exams last year.
B. Whether students who did not receive tutoring this year scored just as highly as those who did.
C. Whether the test assesses topics that are not taught in tutoring sessions offered by schools.
D. Whether the test is consistently as difficult as similar tests.