What function does the control valve in an external tank serve?

The control valve in an external tank plays a crucial role in facilitating the movement of fuel. It allows for the transfer of fuel between the external tank and the aircraft's fuel system. This capability is essential because it ensures that fuel can be moved as needed to maintain optimal balance and performance of the aircraft during flight.

Understanding the specific function of the control valve highlights its importance in fuel management within the aircraft. It does not only regulate the flow but also ensures that fuel can be utilized from external tanks efficiently, helping to meet the operational requirements of the mission.

The other options do touch upon aspects related to fuel handling, but they do not accurately describe the primary function of the control valve. For instance, while monitoring fuel levels is important, it is typically the responsibility of sensors rather than the control valve itself. Similarly, regulating fuel temperature and controlling flow into the tank address different functions that are not directly related to the core purpose of enabling fuel movement.