Which of the terms best describes the process of the production of vapor above the surface of a boiling cargo due to evaporation on an LNG tanker?

Correct Answer: Option A — boil-off

Boil-off refers to the continuous evaporation of cryogenic liquid cargo, such as LNG, caused by heat ingress through the tank insulation. This vapor must be managed by the ship's reliquefaction plant or burned in the boilers or engines to maintain safe tank pressure and prevent over-pressurization of the containment system.