Look back at your answer to the previous question for tube C. Revise your answer to explain why there are more organisms at the top of tube C than at the bottom.

Answer: Tube C contains facultative anaerobes.

Explanation: They can survive with or without oxygen because they can make ATP through anaerobic and aerobic processes. Many facultative anaerobes prefer oxygenated environments, but they can adapt to low-oxygen conditions. This preference is why there are more organisms near the top of the tube.