What is the concentration of Ca²⁺(aq) in a saturated solution of CaCO₃? (Note: The solubility product constant Ksp for CaCO₃ is 4.9 × 10-9.)
A.2.4 × 10⁻⁴ M
B.4.9 × 10⁻⁵ M
C.7.0 × 10⁻⁵ M
D.4.9 × 10⁻⁹ M