We need to find a fact which would weaken the language teachers argument that the courses are a waste of time and money.
b) Schools that have sent students to the 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.
These do not weaken the argument.
e) Since 1995, the number of students who passed the language exams has risen by twenty percent.
This does not explicitly mention that the increase in passing was due to the special courses.
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.
Since the schools which do not send students to special courses were the only ones who participated in the exams prior to 1995 they had better knowledge of the exams and hence had a higher average score. This weakens the argument. So A is the correct answer.