In Evaluating the Data,why Do You Think the Oxygen Levels

In evaluating the data,why do you think the oxygen levels rise and fall over a 24-hour period?

A) Algae in the water produce more oxygen during the daylight hours than the fish consume.
B) The fish consume more oxygen during the nighttime hours than algae can produce.
C) Both of these explain the rise and fall pattern.
D) Neither of these explains the rise and fall pattern.