“Anaerobic” for denitrification requires what condition. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Rates depend on temperature, moisture, substrate quality, consumer physiology, and the elemental balance between organisms and their food. These controls explain why the same process can differ among terrestrial, freshwater, and marine systems without changing its definition. The remaining alternatives—“Aerobic”, “Sunlight”, “Cold temperature”—refer to different states, processes, or scales and
Ref:
Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 18