Feel like these questions are missing details both $in$ the question and $in$ the choices, but might just $beme.$ The Question: If the partial pressure of oxygen in air is $0\mathrm{.}2095$atm, which of the following represents the

concentration of oxygen in air? Assume the pressure of dry air is $1$atm.

$2\mathrm{.}095{10}^{-6}\%$

$0\mathrm{.}2095ppm$

$209,500$ ppm

$2\mathrm{.}1\%$

$209\mathrm{.}5$ ppm