It's A and B i know this probably does not help you now but that the answer for the future people that need it <span />
ANSWER: The war started mainly because of four aspects: Militarism, Alliances, Imperialism and Nationalism. This is because big armies become potential threats to other countries, other countries started forcing alliances in order to secure land. ... The overall cause of World War was the assassination of Archduke Franz Ferdinan
