Dr Rogers Is Eager to Test the Effects of His

Dr. Rogers is eager to test the effects of his newly developed antidepressant drug and would like to administer it to a group of depressed patients to see whether they are less depressed after taking the drug than before. However, a simple "before and after" test of the new drug is inadequate because __________.

A) people differ in the ways they respond to drugs
B) mentally ill participants may forget to take their medication unless supervised
C) spontaneous improvements may be attributed to the drug
D) improvements might not occur until after the second testing