Concept:The key role of vitamin D in the body is to enable the absorption of calcium from the digestive tract, which is vital for maintaining bone density and strength.
Explanation:When you eat calcium‑rich foods, vitamin D acts like a helper that allows your intestines to take calcium into the bloodstream. Without enough vitamin D, most calcium passes out of the body unabsorbed.
Vitamin D also works with calcium to keep bones hard and strong.
Natural sources include sunlight exposure (the best source), oily fish, egg yolks, and fortified dairy products.
A common deficiency leads to soft, weak bones – called rickets in children and osteomalacia in adults. Over time, it increases the risk of osteoporosis and fractures.
Therefore, to maintain healthy bones, both calcium and vitamin D are needed together.
Answer:The correct answer is Vitamin D (Option D).