Before making any welded repairs to the internals of a vessel's fuel tank in a U.S. port, the tank must be examined by __________.

Correct Answer: Option D — a certified marine chemist

Under 46 CFR and OSHA standards, a certified Marine Chemist must inspect and issue a gas-free certificate before any hot work, such as welding, is performed on fuel tanks. This ensures the atmosphere is free of flammable vapors, preventing catastrophic explosions during repair operations in port.