Many high schools send students to special courses to prepare them for language exams. Some language teachers criticize these courses and point out that high schools which do not send their students to special courses have reported a higher average score than those which do since 1995. The language teachers say that the courses are a waste of time and money.
Which of the following, if true, is the most effective challenge to this argument?
A. Those schools which do not send students to the courses have better knowledge of the exams since they are the only schools which participated in the exams prior to 1995.
B. Schools that have sent students to courses since 1995 have experienced a greater drop in their scores than they had prior to 1995.
C. The cost of these courses run by outside teachers has risen dramatically since 1995.
D. The poor design of courses to prepare students for the language exams is not the only reason for their ineffectiveness.
E. Since 1995, the number of students who passed the language exams has risen by 20%.
Please explain your answer.