Question

when you inhale atmospheric nitrogen (n₂), what happens to that nitrogen in terms of the nitrogen cycle?
you convert it into usable nitrogen compounds.
you turn it into nitrates through respiration.
it becomes fixed inside your lungs.
it is unchanged and leaves your body when you exhale.

Explanation:

Humans lack the enzymes required to fix atmospheric nitrogen ($N_2$) into usable compounds. Inhaled $N_2$ passes through the respiratory system without undergoing chemical changes and is exhaled unchanged. The other options are incorrect because humans cannot convert $N_2$ to usable compounds, form nitrates via respiration, or fix nitrogen in the lungs.

Answer:

It is unchanged and leaves your body when you exhale.