Answer:
The correct answer is D. The factor that most contributed to the rise of European militarism in the years leading up to World War I was that military alliances among European states began to rapidly break.
Step-by-step explanation:
The First World War was an event that took place between 1914 and 1918, when the main European powers of the time (and from 1917, the United States) faced each other militarily, after the activation of a series of military alliances previously constituted. Thus, after the assassination of Archduke Franz Ferdinand, Germany, Austria-Hungary and the Ottoman Empire, on the one hand, faced Russia, France, Great Britain and Italy, on the other, and gradually more countries were joining the conflict.