To identify a redox reaction, we must check if there is a transfer of electrons between substances (oxidation and reduction).
Option A:
This is not a redox reaction. It is an equilibrium dissociation of carbonic acid, where no electron transfer occurs.
Option B:
This involves the precipitation of mercury (II) hydroxide but does not involve any electron transfer. Hence, it is not a redox reaction.
Option C:
This is a classic example of a redox reaction, known as cellular respiration. In this reaction, glucose is oxidized to carbon dioxide and oxygen is reduced to water. Thus, electrons are transferred, making it a redox reaction.
Option D:
This is a dissociation reaction, not a redox reaction. There is no electron transfer here.
Thus, the correct redox reaction is Option (C).