Final answer:
Controlled airspace is typically found near airports, cities, and metropolitan areas due to higher levels of official control and the regulation of commercial flight paths by aviation authorities. The correct option is a.
Step-by-step explanation:
Controlled airspace is normally found near airports, cities, and metropolitan areas. This is because the level of official governmental control is usually different in an urban setting from that in rural areas. Moreover, the flight path of a commercial airliner is carefully regulated by the Federal Aviation Administration, ensuring safe distances between planes in these areas. This regulation is crucial due to the concentration of flights around these hubs.
According to the Census, any places that include non-residential urban land uses like factories, businesses, or a large airport, even those that contain few residences, are still counted as part of a city. The Census also considers the incorporation status and surface imperviousness to help classify a place as “urban”. Thus, areas near an urban region with a population density of at least 500 persons per square mile are considered urban, which encompasses many airports and increases the likelihood of controlled airspace.
Hence, Option a is correct.