In the context of enzymes, how does an enzyme affect a chemical reaction?

• A. It increases the activation energy ($E_a$), slowing the reaction while making the reaction more favorable.
• B. It changes the equilibrium constant ($K\equiv \frac{{\left[}_p}{{\left[}_r}$) by stabilizing products more than reactants.
• C. It is consumed during the reaction, so it must be replenished to maintain the reaction rate.
• D. It lowers the activation energy ($E_a$), increasing the reaction rate without changing the overall $\Delta G$ of the reaction.

Answer: (D)