Which mineral salt constitutes a significant portion of bone tissue?

Calcium phosphate is the correct answer because it is the primary mineral component of bone tissue, accounting for about 70% of the bone's weight. It provides bones with their hardness and strength, playing a critical role in the mineralization process that maintains bone density and structural integrity. This compound is crucial for the formation of hydroxyapatite crystals, which are essential for both the rigidity and resilience of bones.

Other substances mentioned, such as magnesium carbonate and sodium chloride, do not significantly contribute to the structure of bone tissue in the same way. Magnesium does play a role in bone health, but it is not a primary constituent. Potassium iodide is primarily related to thyroid function and is not involved in bone composition. Therefore, calcium phosphate is the mineral salt that is most integral to the formation and maintenance of bone tissue.