The solubility of 1:1 salts is measured by the equilbrium constant for the general reaction: MX(s) = Mn+(aq) + Xn-(aq). Given the following salts and their equilibrium constants for the reaction above at 25°C, which salt is the least soluble?
A) MgCO3, Kc = 6.8 × 10-6
B) BaCO3, Kc = 2.6 × 10-9
C) SrCO3, Kc = 5.6 × 10-10
D) CaCO3, Kc = 5.0 × 10-9