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

Multiple Choice

Rate of an enzyme-catalysed reaction as a function of varying reactant concentration, with the concentration of enzyme constant
In the 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 rate of the reverse reaction increases at high reactant concentrations.