Final answer:
Independent DME tuning is most commonly executed through the FMS CDU Tune page, which allows pilots to manually enter and adjust navigation frequencies.
Step-by-step explanation:
Independent DME tuning can usually be carried out via the FMS CDU Tune page. The other options listed, such as the IRS (Inertial Reference System), RMU (Radio Management Unit), and FMC (Flight Management Computer), serve different functions within an aircraft's avionics systems. The FMS CDU Tune page is part of the Flight Management System where pilots can manually enter frequencies for navigation, including DME (Distance Measuring Equipment), allowing for precise control and tuning separate from the automated systems that the FMC might provide.