Final answer:
Under anaerobic conditions, such as during intense exercise, pyruvate is converted into lactic acid, allowing for the continued production of ATP, albeit at lower levels than in aerobic respiration.
Step-by-step explanation:
One physiological source of H⁻ ions is incomplete anaerobic oxidation, resulting in the production of lactic acid. The correct answer to this question is c) Anaerobic, lactic acid.
During anaerobic glycolysis, which occurs when oxygen levels are low or absent, such as during intense exercise, pyruvate is converted into lactic acid.
This conversion helps regenerate NAD* so that glycolysis can continue to produce ATP.
While the amount of ATP produced is less than during aerobic respiration, it allows for the continued production of ATP for short periods of time under anaerobic conditions.