Which of the following sets correctly lists two water-soluble vitamins and two fat-soluble vitamins, with a key function for each?

• A. Water-soluble vitamins: Vitamin C (collagen synthesis) and Vitamin B12 (nerve function); Fat-soluble vitamins: Vitamin A (vision) and Vitamin D (calcium absorption).
• B. Water-soluble vitamins: Vitamin C and Vitamin D; Fat-soluble vitamins: Vitamin A and Vitamin E.
• C. Water-soluble vitamins: Vitamin B6 and Vitamin B2; Fat-soluble vitamins: Vitamin K and Vitamin E.
• D. Water-soluble vitamins: Vitamin C and Vitamin K; Fat-soluble vitamins: Vitamin A and Vitamin D.

Answer: (A)

Vitamins are grouped by solubility: water-soluble ones (like C and the B vitamins) dissolve in water and aren’t stored in large amounts, while fat-soluble ones (A, D, E, K) dissolve in fat and are stored in the body's tissues. A correct set finds two water-soluble vitamins with clear, accurate functions and two fat-soluble vitamins with clear, accurate functions. Vitamin C fits as a water-soluble vitamin with collagen synthesis (and antioxidant roles), and Vitamin B12 is also water-soluble with important nerve function. For fat-soluble vitamins, Vitamin A supports vision, and Vitamin D aids calcium absorption. This pairing matches both solubility and function, making it the best choice. Other options mix up solubility (for example, listing Vitamin D as water-soluble) or omit a specific function for one vitamin.