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?