Which of the following aqueous solutions has the highest freezing point?

An aqueous solution of a salt $MX_2$ at a certain temperature has a van't Hoff factor of $2$. The degree of dissociation for this solution of the salt is

$A^{2+}$,$B^{2+}$ and $C^{-}$ form an ionic complex like $A_{x-2}[B(C)_x]_2$. If the complex is $75 \%$ dissociated in a solvent with $i=4$,the coordination number of $B$ is:

If $1$ mole of a solute dissociates to give $n$ number of ions,then the degree of dissociation $\alpha$ in terms of the van't Hoff factor $i$ is given by:

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 $K_f = 1.86 \ K \ kg \ mol^{-1}$)

In an aqueous solution of $NaCl$,the mole fraction of the solvent is $0.9$. Then,the relative lowering in vapour pressure will be ......... $atm$.