Tooth enamel is primarily composed of hydroxyapatite, with a chemical formula Ca₅(PO₄) ₃OH. When fluoride from fluorinated water or toothpaste reacts with hydroxyapatite, it forms fluorapatite with the formula Ca₅(PO₄) ₃F. The solubility product constant (Ksp) for hydroxyapatite is 6. 8 x 10⁻². Write the expression for the solubility product constant for hydroxyapatite, Ca₅(PO₄) ₃OH.
A. [Ca²⁺][PO₄³⁻][OH⁻]⁵
B. [Ca²⁺]⁵[PO₄³⁻][OH⁻]
C. [Ca²⁺][PO₄³⁻][OH⁻]
D. [Ca²⁺][PO₄³⁻][OH⁻]³