The correct answer is D: FM or PM. FM (Frequency Modulation) or PM (Phase Modulation) is commonly used for VHF and UHF voice repeaters. FM is the standard for repeater operation because it provides good audio quality, is less affected by noise, has a capture effect (stronger signal captures the receiver), and works well with the wide bandwidth available on VHF/UHF. For amateur radio operators, virtually all VHF/UHF repeaters use FM, making it the primary mode for local and regional communications. Understanding this helps when selecting equipment and understanding repeater operations.