Consider the separate solution of $0.500 \mathrm{M} {\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\left(\mathrm{aq}\right),0.100 \mathrm{M} {\mathrm{Mg}}_3{\left({\mathrm{PO}}_4\right)}_2\left(\mathrm{aq}\right),\mathrm{\hspace{0.17em}}0.250 \mathrm{M} \mathrm{KBr} \left(\mathrm{aq}\right)$ and $0.125{\text{ M Na}}_3{\text{PO}}_4\left(\text{aq}\right)$ at ${25}^{o}C$. Which statement is true about these solutions, assuming all salts to be strong electrolytes? 

Osmotic pressure, $\mathrm{\pi }=\mathrm{i}\times \mathrm{MRT}$

Where, i = van't Hoff factor, M = Molarity 

R = gas constant, T = temperature

For 0.500 M ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}$ (aq), i = 1, thus, 

${\mathrm{\pi }}_{{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}}\left(\mathrm{aq}\right)=0.5\mathrm{RT}$

For 0.100 M ${\mathrm{Mg}}_3{\left({\mathrm{PO}}_4\right)}_2\left(\mathrm{aq}\right),\mathrm{i}=5$

$\left[\because {\mathrm{Mg}}_3{\left({\mathrm{PO}}_4\right)}_2\rightleftharpoons 3{\mathrm{Mg}}^{2+}+2{\mathrm{PO}}_4^{3-}\right]$

Thus, ${\mathrm{\pi }}_{{\mathrm{Mg}}_3{\left({\mathrm{PO}}_4\right)}_2\left(\mathrm{aq}\right)}=5\times 0.1\times \mathrm{RT}$

For $0.125{\text{ M Na}}_3{\mathrm{PO}}_4\left(\mathrm{aq}\right),\mathrm{i}=4$

$\left[\because {\mathrm{Na}}_3{\mathrm{PO}}_4\rightleftharpoons 3{\mathrm{Na}}^{+}+{\mathrm{PO}}_4^{3-}\right]$

Thus, ${\text{π}}_{{\mathrm{Na}}_3{\mathrm{PO}}_4}\left(\mathrm{aq}\right)=4\times 0.125\times \mathrm{RT}=0.5\mathrm{\hspace{0.17em}}\mathrm{RT}$

Hence, all solutions have same osmotic pressure.