Can medical oxygen be carried on board during flights?

Medical oxygen can indeed be carried on board during flights under specific conditions, making the selection of this answer appropriate. Passengers who require supplemental oxygen for medical reasons have the option to bring their own oxygen concentrators, which are devices that provide a steady supply of oxygen. However, this is contingent on the aircraft and airline policies, which may require prior notification or approval.

Additionally, having a medical professional accompany a passenger requiring medical oxygen can further ensure that the proper procedures are followed and that the passenger's needs are met safely throughout the flight. This highlights the importance of safety regulations in aviation, especially concerning health-related requirements.

In contrast, the other options do not sufficiently address the conditions under which medical oxygen can be transported. The definitive conditions outlined in option C ensure compliance with regulations while providing necessary support for individuals who require medical oxygen during flight.