Which vitamin is produced in the human body when exposed to sunlight?

1. Vitamin C
2. Vitamin D
3. Vitamin A
4. Vitamin B12

Vitamin D synthesis begins when UVB sunlight converts 7-dehydrocholesterol in the skin to previtamin D₃, which becomes active vitamin D after liver and kidney processing. This vitamin regulates calcium absorption, bone health, and immune function. Deficiency causes rickets in children and osteomalacia in adults.