The best example of a state among the given options is:
"a mountainous region inhabited by heterogeneous ethnicities which share responsibility for maintaining an independent government and a standing army."
This option describes a scenario where there is a recognized governance structure and the elements of statehood, such as a government and military, which are essential characteristics of a state. In contrast, the other options describe various forms of territorial governance or characteristics but do not clearly outline the presence of a formal state structure.