Which of the following aqueous solution will have the boiling point $102.2°\mathrm{C}?$ The molal elevation constant for water is $2.2 \mathrm{K} \mathrm{kg}{ \mathrm{mol}}^{-1}.$

At certain temperature $1.6\%$ solution of an unknown substance is isotonic with $2.4\%$ solution of Urea. If both the solutions have the same solvent and both the solutions have same density $1 \mathrm{gm}/{\mathrm{cm}}^3,$ what will be the molecular mass of unknown substance in $\mathrm{gm} {\mathrm{mol}}^{-1}.$

[Molecular mass of urea $=60 \mathrm{gm} {\mathrm{mol}}^{-1}$]