Which choice most logically completes the text?

According to the passage, the nitrogen-mining hypothesis predicts that the addition of bioavailable inorganic nitrogen will suppress SOM decomposition because microbes will no longer need to scavenge nitrogen from recalcitrant organic matter. Concurrently, the mineral-dissolution hypothesis stipulates that while the pathway is independent of nitrogen, its efficacy strictly requires both abundant iron- or aluminum-bearing minerals and an acidic environment (pH < 5.0). In the experiment, inorganic nitrogen was added (which should suppress nitrogen mining) and the soil was held at a neutral pH of 7.0 (which fails the necessary condition of pH < 5.0 for mineral dissolution). Because SOM decomposition nonetheless increased substantially, the observed priming effect cannot be accounted for by either nitrogen mining or acid-mediated mineral dissolution as defined, logically implying that LOC can accelerate SOM decomposition via an alternative pathway that bypasses the constraints of both models (Choice C).

Choice A is incorrect because the passage explicitly establishes that mineral dissolution requires both mineral presence and an acidic pH; nothing in the text supports the idea that abundant minerals can compensate for non-acidic conditions.

Choice B is incorrect because it commits a partial-elimination error: while inorganic nitrogen indeed suppresses nitrogen mining, mineral dissolution could not have driven the increase because the mesocosm pH was 7.0, violating the necessary condition of pH < 5.0.

Choice D is incorrect because it introduces an unsupported ad hoc reconciliation, inventing an interaction between iron minerals and inorganic nitrogen suppression that is never stated or implied by the text.