It is not reasonable to search out “organic” foods— those grown without the application of synthetic chemicals—as the only natural foods. A plant will take up the molecules it needs from the soil and turn them into the same natural compounds, whether or not those molecules come from chemicals are part of nature, so all are equally natural.
What this question is testing
Conclusion
The author argues against the idea that "organic" foods are the only natural ones.
Evidence
The author's argument: plants make the same compounds whether their inputs come from synthetic fertilizer or not. Anything a plant produces is part of nature. So all foods are equally natural.
Evaluate
Watch what just happened. The author quietly redefined "natural." In ordinary usage (and in the position the author is rejecting), "natural" food means food grown without synthetic chemicals. The author switched it to mean "any compound that exists in nature."
Under the new definition, of course conventionally-grown food counts as natural — almost anything would. But the new definition isn't the one the original claim was using. The author rigged the term in their own favor.
Goal
The right answer will say the author redefines a term in a way that benefits the argument.
Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.