What authorizes an aircraft or vehicle to cross all taxiways that intersect their taxi route?

The correct choice indicates that the absence of holding instructions allows an aircraft or vehicle to cross all taxiways that intersect their taxi route. In air traffic operations, holding instructions are specific directives given to pilots or ground vehicles to hold their position, typically at a taxiway or runway intersection.

When there are no holding instructions in place, this means that the aircraft or vehicle has the authority to proceed along their designated taxi route without interruption. This concept is critical for ensuring safe and efficient movement on the airport surface, as it clarifies when an aircraft can continue to taxi across intersecting taxiways without needing to stop and wait for additional clearance.

The other options would not provide the same level of authority for crossing taxiways. For instance, the presence of a ground controller alone does not automatically grant permission to cross intersections unless specific instructions are issued. Likewise, while Air Traffic Control clearance is essential for various operations, it typically pertains to takeoff, landing, or flight-level changes, rather than surface taxiing unless explicitly stated. Active runway markers are simply indicators and do not provide any authorization for movement; rather, they serve as visual cues for aircraft and vehicles regarding runway boundaries and activity.