The graph shows the changes in lactate and pyruvate measured in an athlete’s blood during and following a mild exercise period as compared to the period before the exercise.

What do these curves suggest?

A. Before the exercise, there was no pyruvate produced because there was no cell respiration.

B. During the exercise, there was not enough oxygen available for cell respiration, so the process was partly anaerobic.

C. During the exercise, the level of lactate increased due to aerobic respiration.

D. After the exercise, the level of lactate decreased because there was enough pyruvate to be used for anaerobic cell respiration.

B