Given the molar solubility of calcium fluoride (CaF₂) is 2.14 x 10^-4 M, calculate its K_sp.

• A. 4.91 x 10^-11
• B. 2.14 x 10^-4
• C. 1.07 x 10^-10
• D. 3.91 x 10^-11

Answer: (D)