c
\(A X_{2}\) is ionized as follows:

\(\underset{\operatorname{mol} L^{-1}}{A X_{2}} \rightleftharpoons A_{s}^{2+}+2 \underset{2 S}{X}^{-}\)

Solubility product of \(A X_{2}\)

\(K_{s p}=\left[A^{2+}\right]\left[X^{-}\right]^{2}=[S] \times[2 S]^{2}=4 S^{3}\)

\(\because K_{s p}\) of \(A X_{2}=3.2 \times 10^{-11}\)

\(\therefore 3.2 \times 10^{-11}=4 s^{3}\)

or, \(S^{3}=0.8 \times 10^{-11}=8 \times 10^{-12}\)

or, \(S=\sqrt[3]{8 \times 10^{-12}}\)

\(=2 \times 10^{-4} \,mol / L\)

Solubility \(=2 \times 10^{-4}\, mol / L\)