Essayist: It would be wrong to defend current testing procedures for new medications simply by appealing to the fact that test subjects are volunteers who are both apprised of and compensated for the risks involved.
Your task
Find the assumption the argument requires in order for its conclusion to hold.
Common trap
Answers that would help the argument but aren't strictly required (sufficient, not necessary).
Winning move
Negate each choice — the right one breaks the argument when negated.