Concept:Millon’s reagent is a chemical test used to detect proteins.Explanation:Millon’s reagent reacts with the amino acid tyrosine, which is present in many proteins.When a protein contains tyrosine, heating it with Millon’s reagent gives a red or pink colour.Therefore, Millon’s reagent is a test for proteins, not carbohydrates, fats, or vitamins.Answer:C. proteins.