Which statement(s) regarding enzyme-catalyzed reactions is/are correct?

I Enzymes contain active sites that cannot be saturated with a substrate regardless of the substrate concentration

II Substrates of enzyme-catalyzed reactions are first-order at low substrate concentrations

III Substrates of enzyme-catalyzed reactions are second-order at high substrate concentrations

A. All statements are correct

B. Only statements I and II are correct

C. Only statements I and III are correct

D. Only statement II is correct

E. All statements are incorrect