Interaction Effects Occur When

Interaction effects occur when

A) there is an imbalance in the experimental and control group at the beginning of an experiment during the pretest.
B) there is experimenter expectancy and there is a diffusion of the treatment at the same time.
C) external validity and reactivity cannot be controlled by a double-blind experimental design.
D) in a factorial design,the impact of two variables operating in combination is greater than each of them added together.
E) instrumental effects cause history effects to get larger and ruin the post-test.