Answer:
A. Germany and Russia
Step-by-step explanation:
It was all started in WWI, the main reason that Austria-Hungary declared war on Serbia, and thus started WWI was the assassination of Archduke Franz Ferdinand on June 28, 1914. Once Austria-Hungary declared war on Serbia, which country supported Serbia and joined in the fight? The archduke of Austria-Hungary was assassinated by Serbian, Gavrillo Princip (from the Black Hand group). Then Germany stepped in to help Austria-Hungary by declaring war on Russia and Russia's ally, France.