In a naphthenic acid corrosive (NAC) environment, what is the effect of sulfur?

According to API RP 571 Section 5.1.3.4 (Naphthenic Acid Corrosion - NAC):

“Sulfur can act as an inhibitor to NAC. Where sulfur content in crude is high, a reduction in naphthenic acid corrosion is sometimes observed, especially in certain parts of vacuum and atmospheric units. However, this is not universally reliable, and corrosion can still occur based on local operating conditions and metal temperatures.”

Thus, Option C (Inhibition) is the correct choice, as sulfur can reduce NAC under some conditions.