Final answer:
The correct answer is B. Acclimatization, which is the body's short-term physiological response to high altitude involving increased production of hemoglobin to compensate for reduced oxygen levels.
Step-by-step explanation:
When an individual from a low-elevation area such as Urbana-Champaign, Illinois, travels to a high-altitude location like Quito, Ecuador, their body undergoes physiological changes to adapt to the reduced oxygen levels. This process is known as acclimatization. At higher altitudes, the air pressure is lower, resulting in a decreased concentration of oxygen. For the body to ensure adequate oxygen delivery to tissues, the kidneys secrete the hormone erythropoietin (EPO), which triggers the production of additional red blood cells. These new red blood cells contain hemoglobin, the protein responsible for transporting oxygen throughout the body.
The increased number of red blood cells raises the body's capacity to capture the available oxygen, even when each hemoglobin molecule's saturation is low. Over time, this adjustment permits individuals to perform physical activities without developing acute mountain sickness (AMS) or other symptoms related to hypoxemia, such as headaches and fatigue. Typically, it takes about 10 days for the body to adjust hemoglobin levels adequately to the new altitude.
Therefore, the correct answer to the student's question is B. Acclimatization.