Question

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

Explanation:

The largest nitrogen reservoir is the atmosphere. Denitrifying bacteria convert nitrates in the soil back into nitrogen gas ($N_2$) which is released into the atmosphere, and volcanic activity also releases nitrogen - containing compounds that can contribute to the atmospheric nitrogen reservoir. Option A (nitrifying bacteria and lightning) is about converting ammonia to nitrates (nitrifying bacteria) and fixing nitrogen (lightning) but not adding to the largest reservoir (atmosphere in terms of release back). Option B (decomposing plant and animal material) is part of the nitrogen cycle but not about adding to the largest reservoir. Option D (nitrates taken up by plant roots) is about plants absorbing nitrates for growth, not adding to the largest reservoir. So the correct option is C as denitrifying bacteria and volcanic activity help add nitrogen to the atmospheric (largest) reservoir.

Answer:

C. Denitrifying bacteria and volcanic activity