What Is One Benefit of Using Controls in an Experiment

Multiple Choice

What is one benefit of using controls in an experiment?

A) The size of the groups can be very large.
B) The subjects do not know anything about the experiment.
C) The subjects who are treated are balanced against the placebos.
D) The subjects are similar in all respects except for the treatment being tested.
E) The costs associated with the study are usually much lower.