【单选题】

The passage supplies information for answering which of the following questions

A、What do historiographers consider to be the precise difference between a nation and a nation-state
B、What concepts in the field of historiography are considered unambiguous
C、Are tribal areas without national spatial markers ever represented as nations
D、What is an example of a nation represented in supra-national units
E、How does the establishment of national spatial boundaries produce political problems