Which feature or technology locks a supervised iPad until it is turned off?

The correct choice is Managed Lost Mode. This feature is specifically designed to enhance the security of supervised devices like iPads by locking them until they are turned off. When a device enters Managed Lost Mode, it becomes inaccessible to anyone who is not authorized, effectively preventing unauthorized use or access to sensitive data. This mode is particularly useful in scenarios where a device is lost or stolen, as it allows administrators to lock the device remotely and display a custom message or contact information on the screen for recovery purposes.

Other options may have their own significance but do not provide the same functionality. Screen Time focuses on usage limitations and monitoring but does not lock the device. A device passcode secures access to the iPad but does not prevent it from being turned on or off. Activation Lock is meant to prevent unauthorized access to the iCloud account associated with the device, but it does not lock the device in the same manner as Managed Lost Mode does. Therefore, Managed Lost Mode stands out as the technology that effectively locks the supervised iPad until it is turned off.