Formal Experiments by Jean-Pierre Leyens and Wendy Josephson on the Effects

Formal experiments by Jean-Pierre Leyens and Wendy Josephson on the effects of watching media violence on aggressive behavior in boys

A) had problems with placebo effects.
B) suggested that watching violence causes real-life violence.
C) proved that the two variables are not correlated.
D) are now believed to be uninterpretable because of experimenter bias.