Answer:
Option C, the closing of the western frontier, is the right answer.
Explanation:
An argument that claimed that American democracy was established by the American frontier came to be known as the Frontier Thesis. This argument was presented by historian Frederick Jackson Turner in the year 1893. He argued that the primary result of the American frontier was American democracy along with a lower interest in high culture, violence and egalitarianism.
Ahy trained historians of Japan in the Western world was too small to
sustain such an enterprise. Although that number has grown, the
general editors have thought it best to draw on Japanese specialists for
contributions in areas where they retain a clear authority. In such
cases the act of translation itself involves a form of editorial cooperation
that requires the skills of a trained historian whose name deserves
acknowledgment.