Instructions:Select each correct answer. More than one answer may be correct.

When an organism eats food containing starch, the starch is broken down into small sugar molecules during digestion in order to obtain energy. This reaction is a type of hydrolysis reaction because it uses water to break down the starch. The enzyme amylase catalyzes the hydrolysis of starch into disaccharides such as maltose.

Amylase activity was studied in the laboratory by conducting an enzyme assay. The following graph shows the rate at which this reaction occurred at different pH values.

Temperature and substrate concentration were kept constant.

Which of the following statements is supported by the graph?

A. The rate of maltose production was highest at point Y.

B. The rate of maltose production was highest at point X.

C. The enzyme was least effective at point Z.

D. The enzyme was more effective at point X than at point Z.