(A) Australia
(B) ** Europe
(C) South America
(D) Antarctica
EXPLANATIONS BELOW
Concept note-1: -Austria-Hungary declares war on Serbia, beginning World War I.
Concept note-2: -World War I, also known as the Great War, began in 1914 after the assassination of Archduke Franz Ferdinand of Austria. His murder catapulted into a war across Europe that lasted until 1918.
Concept note-3: -The assassination of Austrian Archduke Franz Ferdinand on 28 June 1914 set off a chain of events that led to war in early August 1914. The assassination was traced to a Serbian extremist group that wanted to increase Serbian power in the Balkans by breaking up the Austro-Hungarian Empire.
Concept note-4: -Over 30 nations declared war between 1914 and 1918. The majority joined on the side of the Allies, including Serbia, Russia, France, Britain, Italy and the United States. They were opposed by Germany, Austria-Hungary, Bulgaria and the Ottoman Empire, who together formed the Central Powers.
Concept note-5: -World War I began after the assassination of Austrian archduke Franz Ferdinand by South Slav nationalist Gavrilo Princip on June 28, 1914. Read more about why the Balkans became the “powder keg of Europe.”