How does turning off the engine contribute to safety during refuelling?

Turning off the engine during refuelling is crucial for safety primarily because it reduces fire risk. When an engine is running, it produces heat and can create sparks, which may ignite fuel vapors that are present during the refuelling process. Fuel vapors are volatile and can easily catch fire if exposed to an open flame or a spark. By turning off the engine, you eliminate the chance of creating these hazardous ignition sources, thereby significantly enhancing safety for both the operator and the surrounding environment.

The context of other options highlights that while minimizing fuel wastage, preventing engine damage, and ensuring proper ventilation are all important considerations, they do not directly address the critical safety risks associated with fire during the refuelling process. Focusing on fire risk emphasizes the most vital reason why turning off the engine is a standard safety practice in refuelling operations.