When can aircraft be cleared to hold over different fixes at the same altitude?

The correct choice is significant because it highlights the importance of managing air traffic safely and efficiently. When holding pattern airspaces do not overlap, it ensures that aircraft can maintain their respective holding patterns without the risk of intersecting flight paths. This is crucial for preventing potential conflicts and ensuring safe separation between aircraft.

If holding patterns were to overlap, there would be a significant risk of aircraft unintentionally interfering with each other's maneuvers, which could lead to dangerous situations.

In terms of air traffic management, ensuring that holding patterns do not overlap is a key aspect of maintaining order in busy airspace, especially during peak times or when there are delays. By verifying that the holding pattern airspaces are distinct, air traffic controllers can provide clear and safe instructions to pilots while aligning with operational protocols.