Correct Answer:
D. Vitamin D
Vitamin D is uniquely produced in the skin when exposed to ultraviolet B (UVB) rays from sunlight. This process is vital for the body's ability to absorb calcium and phosphorus, which are essential for maintaining strong bones and teeth, and supporting immune function.
- Vitamin A is crucial for vision and immune health but is obtained primarily through diet, not sunlight synthesis.
- Vitamin B refers to a complex of several vitamins (e.g., B1, B2, B12) involved in metabolism and energy production, all acquired through dietary sources.
- Vitamin C is an antioxidant important for immune system function and collagen synthesis, also obtained from food.