How does an inert gas system on a tanker function to prevent explosions in cargo tanks?

Correct Answer: Option D — Inert gas dilutes the flammable vapor and air concentrations to keep them below the lower explosive limit.

By replacing atmospheric air with inert gas, the oxygen concentration in the cargo tanks is reduced below the level necessary to support combustion. This dilution prevents the hydrocarbon-oxygen mixture from reaching its flammable range, regardless of the fuel concentration.