Answer:
C. the American Civil War
Explanation:
When you are doing a research paper, you need to narrow down your topic to a theme that is actually researchable in just a paper, sometime you can narrow it by adding a geographical status, for example, the american civil war in Boston, or a period of time, The Civil War on the year 1862, but the total of the civil war is too broad to be covered, contrary to the other examples like the Battle of Vicksburg, The Buffalo Soldiers and, The Andersonville Civil War prison camp.
