What is required in terms of IFR flight according to ICAO procedures?

In the context of IFR (Instrument Flight Rules) flight according to ICAO (International Civil Aviation Organization) procedures, the correct answer emphasizes requirements for nighttime operations. Specifically, IFR flight is mandated from sunset to sunrise to ensure that pilots operate with appropriate regulatory oversight and safety measures in place during times of lower visibility. This stipulation is important because operations in IFR conditions are significantly affected by reduced light, which could hinder visual navigation and situational awareness.

Operating in IFR conditions generally involves relying on instruments for navigation and control, which is particularly critical during the night when visual references are limited. This enhances safety as pilots must adhere to prescribed protocols and procedures more vigilantly during hours of darkness.

While other options relate to certain operational limits or conditions, they do not encapsulate the specific ICAO requirements governing IFR flight, which prioritize the safety aspects of flying under instrument conditions during those specific hours when visibility may be compromised.