Answer :
The violent act in Bosnia that triggered World War I was the assassination of Franz Ferdinand, the heir to the Austro-Hungarian throne and his wife in Sarajevo on June 28, 1914. The assassin was Gavrilo Princip, a member of a Serbian nationalist group, called Black Hand. The correct answer among the options given above is letter "B."
Your answer is B. The assassination of Archduke Francis Ferdinand.
Hope this helps.
Hope this helps.