(A) Serbia
(B) Italy
(C) ** Austria Hungary
(D) France
EXPLANATIONS BELOW
Concept note-1: -A month after the assassination of Archduke Franz Ferdinand and his wife Sophie on July 28, 1914, the Austro-Hungarian government declares war on Serbia. Immediately, and within a period of six days, European countries declare war upon one another.
Concept note-2: -Austria-Hungary made first declaration of war against Serbia because of assassination of the Austrian Prince Francis Ferdinand and his wife Sophia on June 28, 1914.
Concept note-3: -Telegram of Austria-Hungary‘s declaration of war on Serbia on 28th July 1914. Telegram of Austria-Hungary‘s declaration of war on Serbia on 28th July 1914 marked the beginning of the First World War – one of the world’s most tragic conflicts in the history of human race and initiated the era of unprecedented suffering.