When conducting an experiment for a new heart burn medicine, researchers randomly assigned patients to take either the new drug, an existing heart burn medication, or a placebo. All medications looked the same, and patients were not told which one they received. Was this experiment blinded?

a) No, because the rearchers knew who got which medication
b) No, because it was double blinded
c) Yes, because a control group was used
d) Yes, because the patients don't know which medication they received