What system is designed to prevent over fueling of an aircraft tank?

The volumetric shut off (VTO) system is specifically designed to prevent over-fueling of an aircraft tank by automatically stopping the fuel flow once a predetermined volume of fuel is reached. This functionality is essential for ensuring that fuel tanks are filled to optimal levels without exceeding their capacity, thus reducing the risk of fuel spills and potential hazards associated with over-fueling.

In contrast, while a fuel monitoring system provides data and metrics related to fuel levels and usage, it does not actively prevent over-fueling. The fuel efficiency regulator is more focused on optimizing fuel consumption and performance rather than directly controlling the fueling process. Similarly, the fuel flow optimizer aims to improve the efficiency of fuel flow but is not specifically designed to automatically shut off the fuel to prevent over-filling. Therefore, the VTO system is the most appropriate choice for preventing over-fueling, making it the correct answer.