Regulations require that cargo pumps in tank vessels carrying grade D liquid cargo shall be isolated from sources of vapor ignition by __________.

Correct Answer: Option D — gastight bulkheads

Title 46 CFR requires that spaces containing machinery with potential ignition sources be effectively segregated from cargo pump rooms and tanks. Gastight bulkheads prevent the migration of flammable hydrocarbon vapors into non-hazardous areas, ensuring fundamental safety.