The immediate cause of the outbreak of the First World War is the assassination of the Archduke Ferdinand in Sarajevo on June 28, 1914. The reasons are, of course, much deeper, and the causes should be sought in the interests of the great powers, and the assassination was a trigger, by which Austria-Hungary announced the war to Serbia. In addition to imperialism and militarism, the great contribution to war was given by nationalism. Many ethnic groups within Austro-Hungary wanted autonomy and the creation of national states. The assassination of Archduke Ferdinand was supported by nationalist organizations from Serbia who had an interest in the liberation of Serbs from Austro Hungary and their accession to Serbia. After the war was declared to Serbia by Austro-Hungary, Russia announces the war to Austria wanting to help Serbia, then Germany announces the war to Russia.
The answer is C.
