Factors that affect enzyme action — practice question

The graph illustrates how substrate concentration affects the initial rate of an enzyme-catalysed reaction. The enzyme concentration remains constant. Which statement about the graph is accurate?

• ABetween R and S the number of enzyme molecules is limiting the rate of reaction.
• BBetween R and S the number of product molecules is limiting the rate of reaction.
• CBetween S and T the number of enzyme molecules is limiting the rate of reaction.
• DBetween S and T the number of substrate molecules is limiting the rate of reaction.