During the depression of freezing point in a solution, the following are in equilibrium

The liquid solvent and solid solvent are in equilibrium during the freezing point depression in a solution. Only the solvent freezes out during the freezing of a solution, so an equilibrium exists between the solid and liquid forms of the solvent. The vapour pressures of the solid and liquid forms of the solution must be the same at freezing point, or the system will not be in equilibrium; lowering the vapour pressure leads to lowering the temperature where the vapour pressures of the liquid are the same as that of the frozen forms of the solution.

Therefore Option A is the correct answer