How does carbon dioxide extinguish an aircraft engine fire?

The correct choice is based on the primary mechanism by which carbon dioxide (CO2) extinguishes fires. Carbon dioxide is a non-flammable gas that effectively displaces oxygen in the surrounding atmosphere. Since fire requires oxygen to sustain combustion, when CO2 is introduced into an environment with a fire, it lowers the concentration of available oxygen. This action smothers the flames, effectively interrupting the combustion process and leading to the extinguishing of the fire.

In the context of an aircraft engine fire, using carbon dioxide is advantageous because it can be rapidly deployed and can effectively suppress flames without causing additional damage to sensitive engine components. The ability of CO2 to displace oxygen makes it particularly effective in enclosed spaces, such as engine compartments, where fire risks are elevated.

The other options provide mechanisms that are either less effective or not directly related to how CO2 functions in extinguishing fires. For instance, cooling components can suppress a fire, but it's not the primary action of CO2. Similarly, creating a barrier to prevent ignition or reducing flammable vapors speaks to different fire prevention strategies rather than the direct mechanism of extinguishment that CO2 provides.