Question: What is the primary purpose of supporting the AMR-WB payload format in EVS AMR-WB IO mode, as specified for interoperability?
Option 1: To enhance voice quality for all EVS-supported terminals.
Option 2: To reduce bandwidth usage in EVS communications.
Option 3: To enable communication with terminals that only support earlier versions of EVS.
Option 4: To provide backward interoperability with terminals that support AMR-WB but not EVS.
Explanation: The correct answer highlights the key reason for supporting AMR-WB payload format in EVS AMR-WB IO mode: to ensure seamless communication between EVS-capable devices and those that only support AMR-WB, thereby maintaining interoperability. This is crucial for a smooth transition and coexistence of different technology standards in telecom networks.