People who have migrated from the planes to an area adjoining Rohtang pass about six months back

Answer

A

Explanation

As a person moves up a hill the ` pO_(2)` and total atmospheric pressure decreases. Decrease in `pO_(2)` due to increasing altidue , stimulates the JG cells of kidney to secrete erythrpoetin hromone, increasing the number of RBCs (polycythemia) to compensate the supply of `O_(2)`. At higher atitude haemoglobin has lower binding affinity to `O_(2)` , because the primary factor responsible for binding is `pO_(2)` . which decreases at higher altitude.