Salt Solubilities Can Be Compared by the Concentration of Cation

Salt solubilities can be compared by the concentration of cation formed when the salt dissolves in the general reaction: M_aX_b(s) ⇌ a M^b+(aq) + b X^a-(aq) .Given the following salts and their equilibrium constants for the reaction above at 25°C,which salt is the least soluble?

A) AgCl,K_c = 1.8 × 10^-10
B) Ag₂SO₄,K_c = 1.2 × 10^-5
C) CaCO₃,K_c = 2.6 × 10^-9
D) CaF₂,K_c = 1.5 × 10^-10