Ans. Enzyme concentration.
Enzymes are defined as bio-catalysts that increase the rate of biological reactions by decreasing activation energy of the reaction. Enzymes do not start the reactions, they just speed up the reactions.
During a chemical reaction catalyzed by an enzyme, the total amount of enzymes does not change in anyway or destroyed as it remains constant from beginning to the end of reaction.
Thus, the correct answer is option). 'enzymes concentration.'
