c. A single enzyme typically reacts with many different substrates.
Explanation:
Enzymes are proteins that have catalytic activity and they are specific. This means that a single enzyme has only one specific substrate. They act as a "lock and key" complex, so one substrate activates to one enzyme.
Also, enzymes accelerate the rate of a reaction by lowering its activation energy. Finally, they can act in an aqueous environment, so the answer is c.