At high altitudes, the oxygen content of the air can be one third of the level at sea level. As a person climbs a mountain, the body slowly adapts to the altitude. What increases during this adjustment period?
- Athe concentration of haemoglobin in the red blood cells
- Bthe oxygen-carrying capacity of the haemoglobin
- Cthe number of red blood cells per $ ext{mm}^3$ of blood
- Dthe rate at which haemoglobin releases oxygen to the tissues