Answer: A. Austria-Hungary, Germany and the Ottoman Empire versus Serbia, Russia, France and Great Britain
Explanation: After the assassination of Archduke Franz Ferdinand and his wife Sophie, Austria Hungary sought help from Germany, if, after the ultimatum issued to Serbia, Russia enter into a conflict on the side of Serbia. Since Germany guaranteed help to Austria Hungary, the ultimatum was issued to Serbia, which of course was rejected, followed by a declaration of war to Serbia, Russia entered the war on the side of Serbia, then Germany on the side of Austria, also Western allies enter the war against Germany and Austria Hungary.