Final answer:
The development of a civil airline infrastructure and the operation of airports determine the type of aircraft that can serve them.
Step-by-step explanation:
The subject of this question is Social Studies as it relates to the development of a civil airline infrastructure and the operation of airports.
The grade level of this question is High School as it requires a basic understanding of the subject matter.
The grade of an airport refers to its infrastructure, facilities, and services that determine the type of aircraft able to operate at that airport. This includes factors such as runway length, taxiway width, apron size, and airport equipment. For example, larger airports with longer runways can accommodate larger aircraft like jumbo jets, while smaller airports may only be able to handle smaller regional planes.