Which one of the following alternatives best describes how an age-equivalent score for a standardized achievement test is determined?

a. The student’s performance is compared to standards for the age-group identified by experts in child development.
b. The student’s performance is compared to the average performance of students at various age levels.
c. The student’s performance is compared to that of other students at the same age level, and a percentile score is calculated.
d. The student’s performance is compared to that of other students at the same age level, and a criterion-referenced score is calculated.