Rate of an Enzyme-Catalyzed Reaction as a Function of Varying

Multiple Choice

Rate of an enzyme-catalyzed reaction as a function of varying reactant
Concentration, with the concentration of enzyme constant.
In the accompanying figure, why does the reaction rate plateau at higher reactant concentrations?

A) Feedback inhibition by product occurs at high reactant concentrations.
B) Most enzyme molecules are occupied by substrate at high reactant concentrations.
C) The reaction nears equilibrium at high reactant concentrations.
D) The activation energy for the reaction increases with reactant concentration.
E) The rate of the reverse reaction increases with reactant concentration.