A Double- Blind Placebo- Controlled Experiment Is

A double- blind placebo- controlled experiment is

A) an idea generated by scientists based on their observations.
B) research in which neither the subjects nor the scientists know which group received the treatment and which group received a placebo.
C) research that involves looking at factors in two or more groups of subjects to see if there is a relationship to certain outcomes.
D) a stepwise process used by scientists to generate sound research findings.