People living at sea level have around 5 million RBC per cubic millimeter of their blood whereas those living at an altitude of 5400 metres have around 8 million. This is because at high altitude
A.
atmospheric $${O_2}$$ level is less and hence more RBCs are needed to absorb the required amount of $${O_2}$$ to survive
B.
there is more UV radiation which enhances RBC production
C.
people eat more nutritive food, therefore more RBCs are formed
D.
people get pollution - free air to breathe and more oxygen is available
Answer :
atmospheric $${O_2}$$ level is less and hence more RBCs are needed to absorb the required amount of $${O_2}$$ to survive
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