The keyed exception is “Nitrite.” In the context of which component is not part of the sulfur cycle, that statement differs from the governing ecological pattern and must be evaluated against the mechanism rather than accepted from wording alone. Ecosystem processes are constrained by energy conservation and by the cycling of matter. Energy enters mainly through primary production, is lost as metabolic heat at every transfer, and therefore cannot be recycled in the way that carbon, nitrogen, phosphorus, or water can. The remaining alternatives—“Sulfate”, “Sulfur dioxide”, “Hydrogen sulfide”—re
Ref:
Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 18