A Tourist Who Just Returned from an Extended Mountain Climbing

A tourist who just returned from an extended mountain climbing trip in the Andes is seen in a physician's office for a minor complaint.His blood work reveals a very high hemoglobin level and red blood cell count.The office nurse recognizes this abnormal blood work is associated primarily with:

A) Participation in a vigorous sport over a long time period.
B) Excess consumption of iron-rich raisins in trail mix.
C) Supplemental oxygen used during high-altitude climbing.
D) Chronic hypoxia due to low ambient oxygen at high altitudes.