Cells that live in environments where oxygen is present only a small amount of the time have two options to survive. They can be obligate anaerobes, which are poisoned by oxygen and do full cellular respiration with an electron transport chain that ends in a different molecule than oxygen (such as sulfur.) Alternatively, they can be facultative anaerobes that do full cellular respiration with oxygen when oxygen is available but do fermentation with glycolysis when oxygen is not available. Full cellular respiration makes 32 ATP per glucose. Glycolysis makes only 2 ATP per glucose. Write out which option you think is better in an environment that only occasionally (rarely) contains oxygen, obligate or facultative anaerobe, and defend your answer.