Dr. Whetstone is curious about how self-esteem changes as a result of a new counseling program. She is concerned about testing threats in her study. Which of the following would you recommend to her as a way to address this type of threat? A) Refusing to let participants drop out of the study
B) Conducting a pretest-only study
C) Using a different measure of self-esteem at pretest than at posttest
D) Omitting a comparison group