Which of the following describes the placebo effect? a. Students in art class are not told that their work will be evaluated for a scholarship. b. participants in an experiment do not know if they are in the experimental or control group. c. Participants in a drug study are given an inert pill instead of the drug and behave as though they are given the drug. d. Only females are chosen for a study, even though the population included males. e. Experiments manipulate one variable in a study but not any others.