I would say a because he ran too much but that would be just me I think he hurt his knee from running too much more exercise but probably just aggravate his condition I could be wrong but this is what I think
Answer: To maintain Cellular respiration
Explanation:
The body must take in oxygen so that the blood cells can absorb it. This allows the blood cell to release CO2. Therefore, Inhaling oxygen is necessity for maintaining cellular respiration.
Answer
Explanation: any ways lets get to the answer there is your answer