Which of the following substances shows the highest colligative properties?

$0.8 \ mL$ of acetic acid of density $1.06 \ g \ mL^{-1}$ when dissolved in $1 \ kg$ of water causes a depression in freezing point by $0.0325^{\circ} C$. The Van't Hoff factor is:
$(K_{f} \text{ of } H_2O = 1.86 \ K \ kg \ mol^{-1})$

At a constant temperature,the vapor pressures of aqueous solutions of $Na_2SO_4$,urea,$AlCl_3$,and $1.2 \, m \, KCl$ are approximately equal. The molalities of the aqueous solutions of $Na_2SO_4$,urea,and $AlCl_3$ are,respectively: (Assume $100 \%$ dissociation of the solute)

In which of the following solutions are ions present?

Which of the following pairs has the same freezing point?

What is the freezing point (in $^\circ C$) of a solution containing $0.1 \ g$ of $K_3[Fe(CN)_6]$ (molar mass = $329 \ g \ mol^{-1}$) in $100 \ g$ of water? (Given $K_f = 1.86 \ K \ kg \ mol^{-1}$)