Final answer:
Enzymes have the ability to increase the rates of reactions in living organisms. Factors such as temperature and pH can affect the activity of enzymes.
Step-by-step explanation:
The single most important property of enzymes is the ability to increase the rates of reactions occurring in living organisms, a property known as catalytic activity. Factors such as temperature and pH can affect the activity of enzymes. Temperature changes can disrupt the protein structure of enzymes, while pH changes can also affect their activity. Therefore, option B) The rate of activity of an enzyme might change as pH changes is the best statement that describes enzymes.