A grossly mis-leading question. The question should state if the solubility is to be compared by molarity or grams. If we assume it is to be molar (which is a little easier);
The only way to really do this is to calculate the solubility of each.
Set up an ICE chart for each, substitute into the Ksp expression, and solve for solubility. Then compare.
I can save you some time. All of them will be 4S^3 = Ksp. Solve for S where S stands for solubility in mols/L. You may wish to confirm that each is 4S^3 = Ksp.
Which of the following substances has the greatest solubility in water?
A. Ca(OH)2, Ksp = 6.5 × 10-6
B. Ag2SO4, Ksp = 1.5 × 10-5
C. PbI2, Ksp = 7.9 × 10-9
D. Zn(IO3)2, Ksp = 3.9 × 10-6
E. BaF2, Ksp = 1.5 × 10-6
2 answers
B. Ag2SO4, Ksp = 1.5 × 10-5