Final answer:
The most efficient way to save a PNR or changes is using the online booking system. The system automatically updates and saves the PNR after you confirm the changes. If needed, contacting customer service is an alternative.
Step-by-step explanation:
To save a PNR (Passenger Name Record) or changes to a PNR, the most efficient way is C) Using the online booking system. This allows you to directly access your booking and make necessary modifications, such as updating personal information, selecting seats, adding special requests, or changing travel dates. Once edits are made, the system typically requires you to confirm or accept the changes, which then automatically updates and saves the PNR. In some cases, if the online system does not provide the functionality needed or you encounter difficulties, option A) Contacting the airline's customer service would be the appropriate alternative. They can manually adjust and save changes to your PNR.