An aqueous solution is 0.3 M in ${\mathrm{Al}}^{3+}$ and 3 M in ${\mathrm{Mg}}^{2+}$. Select the only incorrect option. 

Given: $\begin{array}{l}{\left(K_{sp}\right)}_{\mathrm{Al}(\mathrm{OH}{)}_3}=3\times {10}^{-34}\\ {\left(K_{sp}\right)}_{\mathrm{Mg}(\mathrm{OH}{)}_2}=3\times {10}^{-12}{\mathrm{M}}^3\end{array}$

For selective precipitation of $\mathrm{Al}{\left(\mathrm{OH}\right)}_3$ only, pH of solution should be 3 to 8

At $\mathrm{pH} = 9$ both $\mathrm{Al}(\mathrm{OH}{)}_3$ and $\mathrm{Mg}(\mathrm{OH}{)}_2$ will precipitate

At $\mathrm{pOH} = 12$ neither $\mathrm{Al}(\mathrm{OH}{)}_3$ nor $\mathrm{Mg}(\mathrm{OH}{)}_2$ will precipitate

$\mathrm{Mg}(\mathrm{OH}{)}_2$ will precipitate at maximum $\mathrm{pH} = 8$