Answer:
D) Water acts as a reactant.
Step-by-step explanation:
The reactions which break down the polymers into monomers is known as the catabolic reactions. The catabolic reaction which uses water to breakdown the polymers are known as the hydrolysis.
The water is used as a reactant during the breakdown of the polymers as the water splits into the H and OH ions get bonded to the substrate and form the monomer units like in the formation of two molecules of glucose from the maltose.
Thus, D) Water acts as a reactant is a correct answer.