Knowledge of the material covered in the program. One group then watches the program. The control group watches an unrelated entertainment program. A week later, both groups are retested and their scores are compared. In the debriefing discussion afterwards, the research team discovers that many of the teens in the control group looked up the answers to the questions they didn't understand. Which

of the following practices could be used to account for the pre-test influence in future studies?

a. Double blind technique
b. Interrupted time series
c. Reactivity
d. Solomon four-group design

d