Which of the following will have the highest boiling point at $1 \ atm$ pressure?

If a centimolal aqueous solution of $K_{3}[Fe(CN)_{6}]$ has a degree of dissociation of $0.78$,what is the value of the van't Hoff factor?

If sodium sulphate is considered to be completely dissociated into cations and anions in aqueous solution,the change in freezing point of water $(\Delta T_f),$ when $0.01 \ mol$ of sodium sulphate is dissolved in $1 \ kg$ of water,is $(K_f = 1.86 \ K \ kg \ mol^{-1})$ (in $K$).

In a $0.2 \ molal$ aqueous solution of a weak acid $HX$,the degree of ionisation is $0.25$. The freezing point of the solution will be nearest to ......... $^oC$. $(K_f = 1.86 \ K \ kg \ mol^{-1})$

Of the following four aqueous solutions,the total number of those solutions whose freezing point is lower than that of $0.10 \, M \, C_{2}H_{5}OH$ is (Integer answer).
$(i)$ $0.10 \, M \, Ba_{3}(PO_{4})_{2}$
$(ii)$ $0.10 \, M \, Na_{2}SO_{4}$
$(iii)$ $0.10 \, M \, KCl$
$(iv)$ $0.10 \, M \, Li_{3}PO_{4}$

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