Which of the following best states the main point of the passage

(A) The approach to the problem of spatial boundaries is plagued by a number of problems that historiographers are obliged to confront.
(B) Historiographers can benefit from studying the traditional geography of nations in greater depth.
(C) Historiographers should try to refrain from solving the practical issues that arise in the resolution of spatial boundary issues.
(D) The categorization and demarcations of geography at the national level is more complicated than that of the sub-national or supra-national level.
(E) The spatial demarcation of nations is the most complicated issue in contemporary historiography.