Which of the following aqueous solution will exhibit highest boiling point?

Boiling point elevation is a colligative property: $\Delta T_b = i \cdot K_b \cdot m \approx i \cdot K_b \cdot M$. Higher $i \times M$ results in a higher boiling point. Evaluating $i \times M$: (1) Urea: non-electrolyte, $i = 1 \implies 1 \times 0.01 = 0.01$. (2) $\text{KNO}_3$: dissociates into $\text{K}^+ + \text{NO}_3^-$ ($i = 2$) $\implies 2 \times 0.01 = 0.02$. (3) $\text{Na}_2\text{SO}_4$: dissociates into $2\text{Na}^+ + \text{SO}_4^{2-}$ ($i = 3$) $\implies 3 \times 0.01 = 0.03$. (4) Glucose: non-electrolyte, $i = 1 \implies 1 \times 0.015 = 0.015$. Since $0.01\text{ M Na}_2\text{SO}_4$ gives the largest total particle concentration ($0.03\text{ M}$), it exhibits the highest boiling point.