Question

which statement about denitrifiers is true? organisms that act as denitrifiers are exclusively aerobic. they are predominantly prokaryotic archaea. during aerobic respiration, denitrifiers use nitrate or nitrite, rather than oxygen, as the final electron acceptor. they fix atmospheric nitrogen (n₂) into ammonia. they release nitrogen into the atmosphere as nitrogen gas (n₂).

Explanation:

Denitrifiers are bacteria and archaea that convert nitrates and nitrites into nitrogen gas ($N_2$), returning it to the atmosphere. They are not exclusively aerobic, not predominantly archaea, do not use nitrate/nitrite as final electron - acceptor during aerobic respiration, and do not fix $N_2$ into ammonia.

Answer:

They release nitrogen into the atmosphere as nitrogen gas ($N_2$).