Final answer:
The assassination of Archduke Franz Ferdinand of Austria-Hungary caused World War 1.
Step-by-step explanation:
The event that caused World War 1 was the assassination of Archduke Franz Ferdinand of Austria-Hungary. On June 28, 1914, Ferdinand and his wife were assassinated in Sarajevo by a Serbian nationalist. This event sparked a series of political and military alliances that eventually led to the outbreak of the war in 1914.
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