Which of the following is a vitamin?

• A. Vitamin D
• B. Rice
• C. Protein
• D. Lipid

Answer: (A)

Vitamins are organic micronutrients required in small amounts for many bodily processes, often acting as coenzymes or regulators of metabolism. Vitamin D is one of these vitamins, and it’s unique because the body can synthesize it in the skin when exposed to sunlight, with additional sources coming from certain foods or supplements. This combination of being an organic compound needed in small amounts—and not used primarily as an energy source—defines it as a vitamin.

Rice is a source of carbohydrates, providing energy. Protein is a macronutrient made of amino acids essential for growth and tissue repair. Lipid refers to fats, another macronutrient that supplies energy and forms cell membranes. Those are not vitamins, which is why vitamin D is the correct choice.