Answer:
A. The bacteria are breaking down sugars in the absence of oxygen.
Explanation:
Bacteria are microscopic single-celled organims. These organisms may produce their own source of chemical energy, or consume and absorb chemical energy made by producers.
They break down chemical energy like glucose through lactic acid fermentation in their cytoplasm, without the presence of oxygen.
In Glycolysis:
2 molecules of ATP are used to break up glucose into 2 molecules of pyruvate, 4 ATP and 2 electron carrying NADH molecules. Since 2 ATP are used, a net 2ATP are produced by this process.
Then, pyruvate is converted to lactic acid, producing 2 NAD+, used as electron carriers.
