Answer: A) The assassination of the heir to the Austrian throne
Explanation: All offered options except the first one, contributed in the long run to the First World War. The intertwining interests of the colonial powers on the one hand, and the rise of nationalism among the entities in the various empires on the other, have for decades created a tension that will result in a major showdown in WWI.
What was the immediate cause and spark for the beginning of the WWI itself, was certainly the assassination in Sarajevo on June 28, 1914, when Austrian Archduke Ferdinand was killed. After that, Austria Hungary declared war on Serbia, after which great powers entered the war, to the extent of World War.
