Q.

1 molar of urea solution has maximum freezing point.The depression in the freezing point is a colligative property and depends on the number of solute particles present in the solution. All the given solutions have same molarity. However, urea is non electrolyte . whereas NaCl, KCl and CaCl2​ are electrolytes (dissociate in aqueous solution). Hence, 1 molar of urea solution gives least number of solute particles in a given amount of solvent. 1 molar of urea solution has lowest depression in the freezing point and maximum freezing point.