Answer:
b. The assassination of Archduke Franz
Explanation:
The assassination of Archduke Franz Ferdinand was one of the key events that led to World War I. Archduke Franz Ferdinand of Austria, heir presumptive to the Austro-Hungarian throne, and his wife, Sophie, Duchess of Hohenberg, were assassinated on 28 June 1914 by Bosnian Serb student Gavrilo Princip. They were shot at close range while being driven through Sarajevo, the provincial capital of Bosnia-Herzegovina, formally annexed by Austria-Hungary in 1908.