Question

the region of an enzyme molecule that combines with the substrate is the
a allosteric site
b reactant
c active site
d coenzyme
e product

Explanation:

The active - site of an enzyme is the specific region where the substrate binds to the enzyme molecule. Allosteric sites are for regulatory molecules, reactants are the starting substances in a reaction, coenzymes assist enzymes but are not the binding region for substrates, and products are the results of the reaction.

Answer:

C. Active site