The answer is A. Due to the Ottoman Empire’s aggression and that the Balkan states declared independence. With empires like Austria-Hungary and the Ottoman Empire this was the “Power keg of Europe.” After the Death of Franz Ferdinand Austria Hungary declared war of Serbia setting off the power keg. The Ottoman Empire declared war on the allies and helped Austria Hungary.
It's called debt. I think of debt as in the red, the negative zone.
I hope I helped :)
