Answer:
b. Neither the researchers nor the study participants know who is receiving the drug and who is receiving the placebo.
Step-by-step explanation:
In a double-blind test, there are two groups of participants: (1) people who are receiving the new drug and (2) people who are taking a placebo. Neither people from group (1) nor people from group (2) know what they are taking. Also, researchers recollect data from theses groups without knowing which person belongs to each group to avoid any "favoritism" caused by expected results.