Which of the following is least soluble in water?

Solubility product expression of salt $MX_4$ which is sparingly soluble with a solubility $(S)$ can be given as

The molar solubility $(s)$ of zirconium phosphate with molecular formula $(Zr^{4+})_3(PO_4^{3-})_4$ is given by the relation:

At $25^{\circ}C$,the solubility product $(K_{sp})$ of $Zn(OH)_2$ is $10^{-14}$. If $NH_4OH$ is $50\%$ dissociated,what will be the concentration of zinc in a $0.1 \ M$ $NH_4OH$ solution?

Calculate the molar solubility of $Ni(OH)_{2}$ in $0.10 \, M$ $NaOH$. The solubility product constant $(K_{sp})$ of $Ni(OH)_{2}$ is $2.0 \times 10^{-15}$.

$A$ solution containing $0.01 \ M \ Zn^{2+}$ and $0.01 \ M \ Cu^{2+}$ is saturated with $H_2S$ gas. The concentration of $S^{2-}$ is $8.1 \times 10^{-21} \ M$. Given that the $K_{sp}$ values for $ZnS$ and $CuS$ are $3.0 \times 10^{-22}$ and $8.0 \times 10^{-36}$ respectively,which of the following will occur in the solution?