It's a close run between all of the above and C. If I would have to choose, I'd say C, since executing ALL the Spanish seems a bit extreme.<span />
Secret diplomacy was a major factor based on the fact that led to fear between all the nations and confusion. Nationalism and imperialism is a factor, scramble for Africa, Archduke fradana has some ties based that his death lead to more retaliation in the Balkans which wanted to be independents do Austria-Hungary and Russia fought over for.
We know this thanks to archaeologists who excavated many places and discovered that many early civilizations gathered around large rivers where they could develop agriculture. This was seen in places such as Mesopotamia, India, China, Egypt, etc.
