During periods of elevated threat levels, emergency vehicles should not be parked closer than how many feet apart when parking near or in front of airport terminals?

The correct answer is based on the guidelines for maintaining safety and operational effectiveness during elevated threat levels at airports. Parking emergency vehicles at a minimum distance of 10 feet apart ensures that there is sufficient space for rapid deployment and maneuverability in case of an emergency response situation. This spacing reduces the risk of collisions between vehicles, allows for unobstructed access to terminals for passengers and staff, and ensures that assessment and assistance can be provided effectively without any interference.

The other options suggest larger distances, which may not be necessary for emergency scenarios where quick access is vital. While a greater distance could be beneficial in some contexts, for immediate operational needs in an airport environment, 10 feet strikes a balance between safety and functionality, allowing for readiness without extending response times unnecessarily.