A company is evaluating a new language program that is supposed to improve test scores. The box plots show the results of reading tests given before and after using the program. With this data, what is the most reasonable answer to the question: Does the program improve test scores?

a. No, because the low score of 40 and the high score of 80 did not change.

b. No, because the median test score decreased 10 points.

c. No, because some students may have done better on the post-test than on the pre-test.

d. Yes, because the same number of students scored above and below the median on each test.