Three aqueous solutions are prepared at a constant temperature by...

Osmotic pressure is given by $\pi = C R T = \dfrac{w}{M V} R T$

Since the mass of solute $w$, volume of solution $V$, and temperature $T$ are constant for all three solutions, the osmotic pressure is inversely proportional to the molar mass $M$ of the solute.

$\pi \propto \dfrac{1}{M}$

Molar mass of ethylene glycol ($\text{C}_2\text{H}_6\text{O}_2$), $M_1 = 24 + 6 + 32 = 62\text{ g mol}^{-1}$

Molar mass of glycerol ($\text{C}_3\text{H}_8\text{O}_3$), $M_2 = 36 + 8 + 48 = 92\text{ g mol}^{-1}$

Molar mass of glucose ($\text{C}_6\text{H}_{12}\text{O}_6$), $M_3 = 72 + 12 + 96 = 180\text{ g mol}^{-1}$

The order of molar masses is $M_3 > M_2 > M_1$.

Therefore, the increasing order of their osmotic pressures is $\pi_3 < \pi_2 < \pi_1$.

Answer: $\pi_3 < \pi_2 < \pi_1$