In a double-blind, placebo-controlled experiment: a. subjects are assigned to different treatment groups, one of which receives an inactive substance that appears to be a treatment, through random selection.
b. a subject does not know whether he or she received a treatment or an inactive substance.
c. subjects with similar characteristics are assigned to the same group.
d. neither the subjects nor the people administering the treatments know who received a treatment and who received an inactive substance.
e. a subject who received an inactive substance reports an improvement in health or behavior.