A 32 year old high altitude mountaineer is observed to have a hematocrit of 70%. Which of the following represents the most likely cause/explanation
Erythropoietin secretion increases promptly on ascent to high altitude. The increase in circulating red blood cells triggered by the erythropoietin  begins in  2-3 days and is sustained as long as the individual remains at high altitude.
Polycythemia with increased red cell mass
Relative polycythemia due to dehydration
Polycythemia due to hemoconcentration
Polycythemia with high altitude pulmonary edema