The correct answer is C.
During this time, the Balkan Region is controlled by the Austrian-Hungary Empire. Even though they were all under the control of Austria-Hungary, there were many different groups who wanted to develop their own nations free from Austria-Hungary's rule. Conflicts between Serbia and Austria-Hungary lead to constant tensions between the two. Ultimately, the assassination of Archduke Franz Ferdinand resulted in this "powder keg" exploding, starting World War I.