A) create nitrogen gas, but nitrification is aerobic while anammox is anaerobic. B) oxidize ammonia, but nitrification uses O₂ ₐs ₐn ₑlₑctᵣₒn ₐccₑptₒᵣ and anammox uses NO₂-. C) are aerobic processes, but nitrification produces NO₃- and annamox produces N₂ gas. D) occur in soils at neutral pH.