Who is responsible for authorizing the use of the ancillary kit?

The correct choice reflects that the physician on call holds the responsibility for authorizing the use of the ancillary kit. In situations requiring medical assistance during a flight, the physician on call has the necessary training and expertise to assess the medical scenario and determine whether the kit should be utilized. Their authorization ensures that any medical action taken aligns with professional medical standards and protocols, which is crucial for the safety and well-being of the passengers involved.

In contrast, the flight attendant in charge, while trained in emergency procedures, does not have the medical expertise to make such determinations, thus making them less appropriate for this specific responsibility. The pilot in command is primarily focused on flight operations and safety procedures rather than medical decisions. Similarly, the maintenance crew is responsible for the aircraft's physical integrity and operational functionality, but they do not possess medical qualifications needed to assess or authorize the use of a medical kit.