The partial pressure of oxygen in atmospheric air at sea level is equal to the partial pressure of carbon dioxide in atmospheric air at the top of mt. everest. equal to the partial pressure of oxygen in atmospheric air at the top of mt. everest. greater than the partial pressure of oxygen in atmospheric air at the top of mt. everest. equal to the sum of partial pressures from carbon dioxide and nitrogen. less than the partial pressure of oxygen in atmospheric air at the top of mt. everest.

Option C,

Greater than the partial pressure of oxygen in atmospheric air at the top of Mt. Everest.

Explanation:

The atmospheric pressure at sea level is equal to the 760 mm Hg and the corresponding partial pressure for oxygen at sea level is equal to 160 mm Hg.  

With increasing altitude, the oxygen decreases proportionally and therefore its partial pressure also decreases with greater altitudes. The proportionate decrease in oxygen content is 21% and the number of oxygen molecules per breathe is equal to 40%

Hence, option C is correct