Answer: B. Great Britain, France and Russia
Context/explanation:
The military plans laid before World War I presupposed a major war between countries, and the nations of Europe joined together in competing alliances. The Triple Entente had Britain, France and Russia as allies -- and those nations became known as the Allies in the Great War (now known as World War I).
Another alignment of nations, the Triple Alliance, consisted of Germany, Austria-Hungary, and Italy. When the war broke out, Italy changed its allegiance and eventually became part of the Allies. Germany and Austria-Hungary added Bulgaria and the Ottoman Empire to their side in the war, and were known as the Central Powers.