Which of the following solution has the lowest osmotic pressure?

Consider the following equilibrium for benzoic acid in benzene

$2{\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}\rightleftharpoons {\left({\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}\right)}_2$

If $\mathrm{x}$ represents the degree of association of the solute then relationship between total number of moles of particles at equilibrium and van't Hoff factor $\left(\mathrm{i}\right)$ is