Which of the following would exert maximum osmotic pressure?

Osmotic pressure is a colligative property, i.e., depends upon the number of particles of solute. Thus, the solution in which solute gives maximum number of ions, exerts maximum osmotic pressure. Number of particles, (1) In decinormal aluminium sulphate $\mathrm{Al}_2\left(\mathrm{SO}_4\right)_3 \longrightarrow \underbrace{2 \mathrm{Al}^{3+}+3 \mathrm{SO}_4^{2-}}_{5 \text{ particles }}$ (2) In decinormal barium chloride, $\mathrm{BaCl}_2 \longrightarrow \underbrace{\mathrm{Ba}^{2+}+2 \mathrm{Cl}^{-}}_{3 \text{ particles }}$ (3) In decinormal sodium chloride, $\mathrm{NaCl} \longrightarrow \underbrace{\mathrm{Na}^{+}+\mathrm{Cl}^{-}}_{2 \text{ particles }}$ (4) When equal volumes of (2) and (3) are mixed, the concentration becomes half of present concentration. Thus, decinormal aluminium sulphate exerts maximum osmotic pressure.