Dr X Did a Study Showing That Violent Video Games

Multiple Choice

Dr. X did a study showing that violent video games increased aggression, while Dr. Y did a study showing that violent video games did not increase aggression. The most likely explanation is that:

A) the experiment of one or both researchers was invalid.
B) one or both researchers lied about their results.
C) random assignment to groups failed in both experiments.
D) the researchers had different operational definitions of aggression.