What is the floor of the controlled airspace overlying the Coeur D'Alene Airport?

The floor of the controlled airspace overlying Coeur D'Alene Airport is at the surface because it is classified as Class D airspace. In Class D airspace, the controlled airspace extends from the surface up to a designated altitude, typically 2,500 feet above the airport elevation. Since the airspace starts at the surface, this is crucial for managing traffic at airports where both manned and unmanned aircraft operate. Knowing that the controlled airspace begins at the surface allows pilots, including UAS operators, to understand the operating requirements and restrictions in that area, such as communication and visibility rules.

In contrast, the other options propose various altitudes above ground level that do not accurately represent the starting point of the controlled airspace at Coeur D'Alene Airport. This understanding is essential for safe operations near airports and compliance with FAA regulations.