Which of the following $0-10 \mathrm{~m}$ aqueous solutions will have maximum $\Delta T_f$ value?

If boiling point of urea solution is $100.18^{\circ} \mathrm{C}$ and $K_b$ for water is $0.512 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$, molality of solution is (Boiling point of water $=100^{\circ} \mathrm{C}$)

What is osmotic pressure of a semi molar solution at $$27^{\circ} \mathrm{C}$$ ? $$(R=0.082)$$

Solutions $$A, B, C$$ and $$D$$ are respectively 0.2 M urea, $$0.10 \mathrm{~M} \mathrm{~NaCl}, 0.05 \mathrm{~M} \mathrm{~BaCl}_2$$ and 0.05 M $$\mathrm{AlCl}_3$$. All solutions are isotonic with each other except