Which of the following pathways indicate how nitrogen is added to the largest nitrogen reservoir?

A. nitrifying bacteria and lightning

B. decomposing plant and animal material

C. denitrifying bacteria and volcanic activity

D. nitrates taken up by plant roots

Answer:

C. Denitrifying bacteria and volcanic activity

Explanation

The largest nitrogen reservoir is the atmosphere, which consists of about 78% nitrogen gas (N₂). Nitrogen is added back to the atmosphere primarily through denitrifying bacteria and volcanic activity:

Other options describe nitrogen cycling within ecosystems rather than its return to the atmosphere.