After disassembly, the safest way to remove carbon deposits from air compressor inlet and discharge valves is to use __________.

Correct Answer: Option B — diesel oil

Diesel oil is the recommended solvent for cleaning compressor valves because it effectively dissolves carbon deposits and oil residues without damaging metal components. Highly volatile or flammable substances like gasoline or naphtha pose severe fire and explosion hazards in confined machinery spaces and are strictly prohibited for this maintenance task.