How many check valves are found in the fuel system?

The correct number of check valves found in the fuel system is 13. These check valves play a crucial role in ensuring the proper flow of fuel throughout the system by allowing it to flow in one direction while preventing backflow. This is vital for maintaining pressure and ensuring that fuel is delivered efficiently to the engines. The specific number may vary depending on the configuration and design of the aircraft's fuel system, but in this context, the standard setup includes 13 check valves strategically placed to optimize performance and safety.