Why are these studies effective for testing a drug that may elevate mood and relieve feelings of depression?

B)Double-blind studies are ways to ensure that only the researcher can figure out who is getting the effective drug. This is to help and maintain the objectivity of the study especially because since it concerns humans as test subjects. Moreover, it is also to avoid biases and errors which can be elicited by either the researcher himself or the participants.

The correct answer is a. we know this because n (hap) + n (hap) = 2n (dip).