A researcher suspects that a new popular food supplement has substantial negative health effects. What procedure would be most appropriate for a study aimed at
clarifying this issue?

A. Recruit volunteers from the local college and randomly assign them to the groups that will and will not consume the supplement.

B. Recruit volunteers through a local radio station and randomly assign them to the groups that will and will not consume the supplement.

C. Recruit volunteers from the shoppers at the local health food store and randomly assign equal numbers of men and women to the groups that will and will not consume the supplement.

D. Recruit volunteers through a local newspaper and assign them to two groups according to whether they have used the sup ement or not.