Why does the predictive validity of general aptitude tests decrease as the educational level of the students who take them increases?

a. More educated students have taken aptitude tests so frequently that for them such tests are no longer pure measures of aptitude.
b. Comparisons of mental age with chronological age are inadequate for assessing the aptitude of older and more educated students.
c. There is a relatively restricted range of aptitude test scores among students at higher educational levels.
d. Among more educated students, motivation has a much greater effect on academic success than does aptitude.

Answer: c. There is a relatively restricted range of aptitude test scores among students at higher educational levels.