Placebo Groups Are Often Used in Multigroup Designs Because

Placebo groups are often used in multigroup designs because:

A) they are cost effective because you don't have to purchase an additional treatment for participants.
B) they help determine how much the participants' responses are due to their expectation rather than the treatment itself.
C) they help determine the true score for participants on the dependent variable in relation to the response to treatment.
D) they are required in order to conduct a comprehensive multigroup design.