To Avoid the Use of Deception in His Experiment,a Researcher

To avoid the use of deception in his experiment,a researcher tells participants ahead of time that they will be witnessing a staged fight between two people who were actually confederates of the experimenter.By so informing the participants,this researcher has decreased the ________ realism of his experiment.

A) psychological
B) internal
C) mundane
D) ethical
E) experimental