Final answer:
Oxygen debt is the extra amount of oxygen needed after strenuous exercise to restore the body to its pre-exercise state, as a result of lactic acid buildup in the muscles that needs to be oxidized.
Step-by-step explanation:
The term oxygen debt refers to the extra amount of oxygen the body needs after strenuous exercise to restore all systems to their pre-exercise states. Among the given options, the true statement about oxygen debt is that D. Oxygen debt develops owing to lactic acid buildup within a person's muscles, requiring oxidation of high levels of oxygen. This occurs because during intense exercise, when oxygen supply to the muscles is insufficient for the demands, anaerobic respiration takes place, and lactic acid is produced as a byproduct. After the exercise, oxygen is needed to convert the lactic acid back to pyruvic acid, restore ATP and creatine phosphate levels, and in the liver, convert lactic acid to glucose or glycogen. The increased rate of breathing post-exercise is an indication that the body is repaying this oxygen debt.