In which of the following solution the depression in freezing point is lowest?

• Correct answer
  A

  0.2 M urea and 0.2 M glucose
• B

  0.1 M $\mathrm{A}{\mathrm{l}}_2(\mathrm{S}{\mathrm{O}}_4{)}_3$ and 0.1 M $\mathrm{N}{\mathrm{a}}_2\mathrm{S}{\mathrm{O}}_4$
• C

  0.1 $\mathrm{M}\mathrm{K}\mathrm{N}{\mathrm{O}}_3$ and 0.2 M $\mathrm{B}\mathrm{a}(\mathrm{N}{\mathrm{O}}_3{)}_2$
• D

  0.1 M $\mathrm{C}\mathrm{a}(\mathrm{N}{\mathrm{O}}_3{)}_2$ and 0.1 M $\mathrm{B}\mathrm{a}(\mathrm{N}{\mathrm{O}}_3{)}_2$

Hence, the correct answer is option: 'A'.