Final answer:
Mountain climbers return to lower elevations to acclimatize to the lower oxygen levels in higher elevations, preventing severe symptoms of hypoxia.
Step-by-step explanation:
Mountain climbers continuously return to lower elevations before climbing into hypoxic conditions to allow their bodies to acclimatize and adjust to the lower oxygen levels. As they ascend to higher elevations, the oxygen concentration in the air decreases, leading to inadequate supply of oxygen to the body, known as hypoxia. To counteract this, the body responds by producing more hemoglobin, which takes about 10 days to adjust to the new altitude. By descending to lower elevations periodically, climbers give their bodies time to adjust and prevent severe symptoms of hypoxia.