Which one of the following 0 . 06   M aqueous solutions has lowest freezing point ?

${\mathrm{T}}_{\mathrm{f}}^{\circ }-{\mathrm{T}}_{\mathrm{f}}={\mathrm{iK}}_{\mathrm{f}}·\mathrm{m}$

${\mathrm{T}}_{\mathrm{f}}$ = Freezing point of the solution.

$\mathrm{i}=$Van 't Hoff factor

${\mathrm{K}}_{\mathrm{f}}$ = molal freezing point depression constant

$\mathrm{m}=$molality
For minimum ${\mathrm{T}}_{\mathrm{f}}$,  $\mathrm{i}$ should have the maximum value.

$\begin{array}{cc}{\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3& \mathrm{i}=5\\ {\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6& \mathrm{i}=1\\ \mathrm{KI}& \mathrm{i}=2\\ {\mathrm{K}}_2{\mathrm{SO}}_4& \mathrm{i}=3\end{array}$