7 a.m. 2 p.m. 9 p.m. midnight
I gave my students this multiple choice question: Coral reefs are found in shallow tropical ocean waters. A coral reef is a diverse ecosystem that is supported by the photosynthesis of marine plants and the algae that live within the tissues of the coral. Given this information, when would the waters in a coral reef likely have the highest dissolved oxygen concentration?

Only one answer is correct among these 4 choices:
- 7 a.m.
- 2 p.m.
- 9 p.m.
- midnight

Could you tell me which one is correct?

2 p.m.