People living in high altitudes (like mountains) usually have a _________?
- A. smaller number of Red Blood Cells
- B. larger number of Red Blood Cells
- C. smaller number of White Blood Cells
- D. larger number of White Blood Cells
Explanation
At high altitude, lower oxygen pressure stimulates the kidneys to release erythropoietin, increasing red blood cell production. The extra red cells help carry more oxygen to tissues.