Final answer:
The benefits of acclimatization are typically lost within 2-3 weeks after returning to sea level, as the body's physiological adaptations to high altitude fade without continued exposure.
Step-by-step explanation:
The benefits of acclimatization to high altitudes, which often include adjustments such as increased red blood cell count and higher breathing rates, tend to be lost after returning to sea level. These physiological adaptations can disappear if not maintained by continued exposure to high altitude conditions. The correct answer to the question is a) Within 2-3 weeks, this is the typical time frame in which the body starts losing the acclimatization benefits after leaving a high-altitude environment.