which of the following best explains the role of a city under central place theory?
a. a city marks the minimum provision needed for central place to be economically reasonable in a given area
b. a city serve a function beyond its immediate area by performing services integral to the world economy
c. a city provides for a specific ranking of different central places depending on their size
d. a city exist above a threshold and under a range of economic production as it provides for its surrounding market area