The correct answer is option b. higher levels of hemoglobin.
The partial pressure of the oxygen decrease as the height from the sea level is increased. Due to the decrease in the partial pressure, the amount of the oxygen delivered by the hemoglobin to cell decrease. So, in order to cope up the condition, the amount of the hemoglobin in the blood is increased. the increased amount of the hemoglobin delivers more oxygen than the normal amount of hemoglobin can do, so, it help in survival at low oxygen levels.
The benefits are the reproduction of organisms
3. maintain internal stability
Yes it is the best way to prevent jerm spreadage
