Marco Leyton,a Psychology Professor at McGill University,began to Study the Effects

Marco Leyton,a psychology professor at McGill University,began to study the effects of cocaine on the human brain.To be considered a potential participant in his research,agreement of all of the following was expected EXCEPT:

A) you are fully informed about the study and give consent.
B) you cannot be a previous user of cocaine.
C) you are a previous user of cocaine.
D) you are required to stay overnight so the doctors and nurses can continue to monitor you.