Why is phosphorus important alongside calcium for bone mineralization?

• A. Phosphorus is only a waste product in bone that must be removed regularly to maintain bone strength and does not participate in mineral formation.
• B. Phosphorus acts solely as an intracellular signaling molecule in neurons and has no structural or mineral role in skeletal tissue.
• C. Phosphorus prevents osteoblasts from producing collagen and therefore reduces the organic matrix allowing pure calcium crystal deposition only in cortical bone.
• D. Phosphorus combines with calcium to form hydroxyapatite crystals (calcium phosphate), which are the mineral matrix that gives bone its rigidity and strength.

Answer: (D)