Which of these compounds is the least soluble in water?
CaF₂ (Ksp = 3.5 x 10⁻¹¹)
FeF₂ (Ksp = 2.4 x 10⁻⁶)
Ag₂SO₄ Ksp = 1.3 x 10⁻⁵) BaSO₄ (Ksp = 1.1 x 10⁻¹⁰)

O CaF₂
O FeF₂
O Ag₂SO₄
O BaSO₄