GMAT Critical Reasoning (CR) | Re: Seventy-five percent of the subjects in an experiment consumed only

Background : Seventy-five percent of the subjects in an experiment consumed only organic foods grown without the use of pesticides.
Premise : After a two-year period of the study, this group exhibited significantly high immunity to the common cold and flu than did the other subjects - the control group - who did not consume only organic foods.
Conclusion : The positive effects of organic foods were attributed to the absence of both harmful pesticides used in growing non-organic fruits and vegetables,
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