What do Visual Flight Rules (VFR) refer to?

Visual Flight Rules (VFR) refer to flight rules that enable pilots to navigate and operate their aircraft visually, rather than relying solely on instruments or radar systems. Under VFR, pilots must maintain visual reference to the ground and other landmarks to ensure safe navigation, which also involves adhering to visual meteorological conditions (VMC) that provide sufficient visibility and avoid obstacles.

While B emphasizes the aspect of visual navigation, it is important to note that VFR does not strictly limit flight operations to clear weather, as some pilots may still operate VFR in marginal conditions as long as they can maintain visual reference and meet regulatory visibility requirements. Therefore, while certain flight operations under VFR are indeed more manageable in clear weather, it is not an exclusive requirement. The other options would refer to concepts that do not accurately define VFR; for example, radar navigation is associated with Instrument Flight Rules (IFR), while nighttime flying and specific weather conditions may still allow for visual navigation depending on the pilot's visibility and judgment on safety. Thus, B correctly encapsulates the essence of VFR, which is fundamentally operated based on a pilot's ability to see the outside environment.