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

The pathways that indicate how nitrogen is added to the largest nitrogen reservoir, the atmosphere, include:

1. Biological nitrogen fixation: This is the process where certain bacteria and archaea convert atmospheric nitrogen gas (N2) into ammonia (NH3) using the enzyme nitrogenase. This process adds biologically usable nitrogen to the ecosystem but actually consumes nitrogen from the atmosphere rather than adding atmospheric nitrogen.
2. Lightning: Lightning causes nitrogen gas (N2) and oxygen (O2) in the atmosphere to react, forming nitrogen oxides (NOx), which eventually contribute to nitrogen compounds that return to the soil and water and recycle nitrogen. This process adds reactive nitrogen compounds derived from atmospheric N2.
3. Volcanic activity: Volcanic eruptions release nitrogen gases and nitrogen compounds into the atmosphere, thereby adding nitrogen to this reservoir.

The largest nitrogen reservoir is the atmosphere primarily composed of nitrogen gas (N2). These pathways contribute to adding reactive nitrogen to or cycling nitrogen within the atmosphere and biosphere. In summary, the key pathways adding nitrogen to the largest nitrogen reservoir, the atmosphere, are lightning and volcanic action, while biological nitrogen fixation converts atmospheric nitrogen into biologically usable forms but does not add nitrogen to the atmosphere itself.