There is a step in the traditional production process of aged vinegar.

A, the solute of mature vinegar is acetic acid, not alcohol, which cannot be expressed by the chemical formula of alcohol. The options are optional.

B, the three-state change of matter is a physical change, and the freezing of water is a physical change, so the option is not optional.

C, evaporation is the reduction of water, that is, the reduction of solvent, which makes the solution thicker, so this option is not optional.

D. Fishing in winter and drying in summer is actually a way to reduce the amount of solvent and improve the mass fraction of solute, so this option is not optional.

So choose one