Final answer:
During rest, only about 20% of the oxygen is utilized, as opposed to a potential 100% during exercise.
Step-by-step explanation:
During rest, only about 20% of the oxygen is utilized, as opposed to a potential 100% during exercise. The process of utilizing oxygen to produce energy through the breakdown of glucose or other nutrients is called aerobic respiration. This process produces approximately 95% of the ATP required for resting or moderately active muscles.