Which one of the following will exert highest osmotic pressure

Osmotic pressure is $\pi =\mathrm{iCRT}$

where,

$\pi =$osmotic pressure of the solution

$\mathrm{i}=$ Van't hoff factor $=1$ (for non-electrolytes)

$\mathrm{R}=$ Gas constant

$\mathrm{T}=$ temperature of the solution

osmotic pressure directly proportional to no. of solute$\left(\mathrm{i}\right)$ as all have same concentration.

 So, For Glucose(non-electrolyte), $\mathrm{i}=1$

             Urea(non-electrolyte), $\mathrm{i}=1$

             Alum, $\mathrm{i}=3$

             NaCl, $\mathrm{i}=2$

Therefore, Alum has the highest osmotic pressure because the colligative ions are the most in it and it will exert the highest osmotic pressure due to a large number of ions or particles.

Hence, option(c) is correct.