The correct answer is C) Inert gas dilutes the flammable vapor and air concentrations to keep them below the lower explosive limit. An inert gas system on a tanker functions to prevent explosions in cargo tanks by reducing the concentration of oxygen in the tank atmosphere. By injecting an inert gas, such as nitrogen or carbon dioxide, the system lowers the oxygen content below the level required to support combustion, typically below 8% by volume. This effectively dilutes the flammable vapors, keeping the overall mixture below the lower explosive limit and preventing the formation of an explosive atmosphere in the tank. The other options are incorrect because they do not accurately describe the primary mechanism by which an inert gas system prevents explosions. Option A is incorrect as it refers to a "charged mist" effect, which is not related to the function of an inert gas system. Option B is incorrect as maintaining a positive pressure is not the main purpose of the system, and cooling the vapors is not the primary means of explosion prevention. Option D is incorrect as the inert gas does not filter out the flammable vapors, but rather dilutes the overall mixture to a non-explosive level.