Correct answer: C. France, Russia, and Great Britain.
Context:
The days leading up to the Great War (World War I) were full of military buildup, military planning, and countries lining up with one another in alliance systems. The Triple Entente had Britain, France and Russia as allies. In between those countries were the members of the Triple Alliance: Germany, Austria-Hungary, and Italy.
Because of the alliance system, Germany assumed that if a war began, it would need to fight on two fronts -- west and east. So German Field Marshall Alfred von Schlieffen drew up war plans that said attack France first, quickly, and then hold that territory while deploying forces to contend with Russia in the east. So when Germany declared war on Russia in 1914, the first thing it did was to go and attack France. Thus the war spread and became instantly a more global conflict.
