Humans have difficulty obtaining enough oxygen while breathi

Humans have difficulty obtaining enough oxygen while breathing at high elevations because _______ at low elevations.

CO2 makes up a higher percentage of the air than it does

the barometric pressure is higher than it is

the air is drier than it is

the partial pressure of O2 is lower than it is

Solution

Humans have difficulty obtaining enough oxygen while breathing at high elevations because the partial pressure of O2 is lower than at low elevations. The air pressure is 30% lower at higher altitude due to the fact the atmosphere is less dense and the air molecules are further apart. So the pressure decreases with increasing altitude as there are fewer air molecules at higher level.