Amine stress corrosion cracking is most likely to occur in what services?

From API RP 571 Section 5.1.2.7 (Amine Stress Corrosion Cracking) and API RP 945 (Avoiding Environmental Cracking in Amine Units):

MEA (Monoethanolamine) systems are most aggressive due to:

“Their high reactivity and degradation potential producing corrosive by-products that promote cracking.”

API RP 945:

“SCC in carbon steel is most frequently reported in MEA units, especially where localized concentrations of heat-stable salts exist.”

Thus, Option C (MEA) is the correct answer due to its high SCC risk.