What is the minimum altitude a pilot must maintain during an off-airways IFR flight over non-mountainous terrain?

In an off-airways IFR flight over non-mountainous terrain, the regulation states that a pilot must maintain a minimum altitude of 1,000 feet above the highest obstacle within 4 nautical miles of the course. This requirement is primarily designed to ensure a safe vertical separation from any terrain or obstacles that could pose a risk to the aircraft during flight. Keeping this altitude helps in avoiding collisions with both natural and man-made structures, particularly in areas where navigation does not rely on established airways.

The choice of maintaining this altitude provides a buffer that allows for changes in terrain elevation and ensures that the aircraft has sufficient altitude to conduct safe maneuvers if required. Therefore, option A aligns perfectly with the safety standards set by aviation regulations for IFR flights over non-mountainous areas.