Final answer:
The correct answer to the student's question is 'd) Airport maintenance protocols', which ensure runway safety through tasks such as lighting inspections, critical area signs placement, and the availability of secondary power for RVOP situations.
Step-by-step explanation:
The procedures that apply to runway operations and approaches, which include lighting inspections, critical area signs placement, and ensuring operational secondary power for potential Reduced Visibility Operations Plan (RVOP) requirements, are best categorized as airport maintenance protocols. These protocols are critical for the safety and efficient operation of an airport. Lighting inspections ensure that pilots have clear visual guidance, especially during times of low visibility. Placement of critical area signs serves to protect sensitive Instrument Landing System (ILS) areas from interference. Ensuring the availability of operational secondary power is essential for maintaining airport operations during outages, which may become crucial during RVOP situations when visibility is compromised.