6. What type of quasi-experimental design best fits the following scenario: A school counselor wanted to see if interest in seeking a college degree changes across one's high school career. She measures interest in a group of students across all four years to see if there is a measurable change.

a. single group posttest-only

b. non-equivalent control group pretest/posttest

c. single-group pretest / posttest

d. single group time-series