Why Was the Choice of Subjects for the Willowbrook Study

Why was the choice of subjects for the Willowbrook study unethical?

A) The subjects were all from the same school, so the study results could not be applied to the general population.
B) The subjects were given the experimental treatment whether they had hepatitis or not, which could have harmed the control group.
C) The subjects were all adolescent minors who had mental disabilities and were not competent to give informed consent.
D) All of the above.