https://wisdomessays.com/wp-content/uploads/2020/07/logo-300x60.png00adminhttps://wisdomessays.com/wp-content/uploads/2020/07/logo-300x60.pngadmin2020-08-20 23:47:002020-08-20 23:47:00Why does a mountain climber need an oxygen supplyat very high altitudes,even though the air still contains 21% oxygen?