A Biochemist Generates an Enzyme Activity Curve for an Unknown

A biochemist generates an enzyme activity curve for an unknown enzyme.The curve is shown below. Which statement best explains the shape of this curve?

A) The enzyme has multiple active sites. As the enzyme binds substrate at one site, its affinity for binding substrate at other active sites increases.
B) The enzyme has a single active site. As the enzyme binds substrate, the activity of the enzyme stalls until it can clear the active site.
C) The enzyme has multiple active sites. As the substrate concentration increases, all sites must be equally bound for the reaction to proceed.
D) The enzyme has multiple active sites. Substrate binding at each of the sites is dependent upon the temperature of the reaction.
E) The enzyme has a single active site. Substrate binding at this particular site occurs within a narrow pH range, termed the equivalence point.