In the context of environmental contaminants, which statement describes the meaning of an "added" substance in food as the term is used in the Food, Drug, and Cosmetic Act 402(a)(1) definition of adulterated food?
a) Introduced by mankind into the environment.
b) A pesticide residue that exceeds the EPA tolerance.
c) Artificially added to food.
d) An unapproved food additive.