The Purpose of a Follow-Up Observations Is To

The purpose of a follow-up observations is to:

A) Allow additional time to locate original research participants to maximize sample size at post-test.
B) Assess the normal amount of change that occurs between two measurements before the introduction of the independent variable.
C) Determine whether observed differences between the pre-test and the post-test are maintained over time.
D) Assess the amount of change that occurs between two measurements after the introduction of the independent variable.