(A) France
(B) ** Austria-Hungary
(C) Italy
(D) Russia
EXPLANATIONS BELOW
Concept note-1: -On May 23, 1915, Italy declares war on Austria-Hungary, entering World War I on the side of the Allies-Britain, France and Russia.
Concept note-2: -Austria-Hungary, with German encouragement, declared war on Serbia on 28 July. Russia’s support of Serbia brought France into the conflict. Germany declared war on Russia on 1 August and France on 3 August.
Concept note-3: -The immediate reason for Austria’s ultimatum was the assassination of Archduke Franz Ferdinand and his wife Sophie in Sarajevo, Bosnia on June 28, 1914 by the Bosnian Serb nationalist, Gavrilo Princip.