Which unit can be used to tune the VHF navigation radios?

The Flight Management System (FMS) is the correct choice for tuning VHF navigation radios because it is specifically designed to manage navigation and flight planning data within the cockpit. The FMS integrates various navigation sources, allows for the input of waypoints, and facilitates automated flight routing. One of its critical functions includes the ability to tune various navigation radios, including the VHF navigation radios.

The other systems listed have different roles. The Autopilot System primarily focuses on maintaining aircraft flight paths and does not handle tuning radios. The Engine Control Unit is responsible for managing engine performance and does not interact with navigation systems. The Electronic Flight Instrument System (EFIS) displays flight data and information to pilots but does not provide the functionality to tune radios; instead, it works in conjunction with systems like the FMS to present that data.