Multiple choice

In high altitude, the ______.

  1. number of RBC increases

  2. size of RBC increases

  3. number of RBC decreases

  4. size of RBC decreases
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

At high altitudes, decreased atmospheric oxygen partial pressure triggers increased erythropoietin production, which stimulates red blood cell (RBC) production in bone marrow. This adaptive response, called polycythemia, improves oxygen-carrying capacity. The RBC count increases, not the size. Options C and D are incorrect as RBC count increases, not decreases. Size changes are not the primary adaptation.

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