MrSmith Moved from a Low Altitude to a High Altitude

Multiple Choice

Mr.Smith moved from a low altitude to a high altitude and experienced an increase in RBCs.Which of the following caused this increase?

A) the lower temperature present at higher altitudes
B) the lower oxygen concentration seen at higher altitudes
C) the increased metabolic rate seen at higher altitudes
D) the increased CO₂ retention that occurs at high altitudes
E) He exercised more.