Question

which statement about denitrifiers is true? they fix atmospheric nitrogen (n₂) into ammonia. 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 release nitrogen into the atmosphere as nitrogen gas (n₂).

Explanation:

Denitrifiers are bacteria that convert nitrates into nitrogen gas ($N_2$), returning it to the atmosphere. Nitrogen - fixing bacteria fix atmospheric nitrogen into ammonia. Denitrifiers are often anaerobic or facultative anaerobic. They are mainly bacteria, not predominantly archaea. During anaerobic respiration (not aerobic), they use nitrate or nitrite as the final electron acceptor.

Answer:

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