The solubility products of $\mathrm{A}\mathrm{l}(\mathrm{O}\mathrm{H}{)}_3$ and $\mathrm{Z}\mathrm{n}(\mathrm{O}\mathrm{H}{)}_2$ are $8.5\times 10^{-23}$ and $1.8\times 10^{-14}$ respectively. If $\mathrm{N}{\mathrm{H}}_4\mathrm{O}\mathrm{H}$ is added to a solution containing $\mathrm{A}{\mathrm{l}}^{3+}$ and $\mathrm{Z}{\mathrm{n}}^{2+}$ ions, then substance precipitated first is:

• Correct answer
  A

  $\mathrm{A}\mathrm{l}(\mathrm{O}\mathrm{H}{)}_3$
• B

  $\mathrm{Z}\mathrm{n}(\mathrm{O}\mathrm{H}{)}_2$
• C

  Both together
• D

  None at all

Hence, the correct answer is option: 'A'.