Nitrogen oxides are formed naturally by which of the following processes?

Nitrogen oxides, such as nitrogen dioxide (NO2) and nitric oxide (NO), are primarily formed through natural processes involving biological reactions. One significant process occurs during the bacterial consumption of nitrogenous materials, particularly through nitrogen-fixing bacteria present in the soil. These bacteria convert atmospheric nitrogen (N2) into forms that can be utilized by plants, such as nitrates and nitrites. This process can lead to the formation of nitrogen oxides as a byproduct.

In contrast, photographsynthesis primarily involves the conversion of carbon dioxide and water into glucose and oxygen, not nitrogen oxides. Land combustion typically refers to the burning of fossil fuels or biomass, which is a human-induced process and not a natural formation of nitrogen oxides. Lastly, the evaporation of water pertains to the hydrological cycle and does not relate to nitrogen compounds directly, as it does not contribute to the formation of nitrogen oxides. Thus, the process of bacterial consumption of nitrogenous materials is the correct natural formation mechanism for nitrogen oxides.