Among the following, the aqueous solution with the lowest freezing point is

According to colligative properties of solutions, the compound which can produce more number of ions in solution that will have lowest freezing point. Among the give all solutions ${\mathrm{CaCl}}_2$ will undergo ionization and that will give total three ions $\left(1{\mathrm{Ca}}^{+2},2{\mathrm{Cl}}^{-}\right)$Therefore, 0.1 m solution of ${\mathrm{CaCl}}_2$ have the lowest freezing point.