Sulfidation of iron-based alloys usually:

API RP 571 and RP 939-C define sulfidation conditions as:

“Sulfidation of iron-based alloys generally becomes significant at temperatures above 500°F (260°C) in hydrocarbon streams with sulfur but without hydrogen.”

“For hydrogen-containing environments, this threshold may be reduced to 450°F (230°C).”

(Reference: API RP 571, Section 4.2.1.1 – Sulfidation; API RP 939-C, Section 3.1)

Therefore, the correct answer is D.