The correct option is
•it led to the assassination of the archduke of Austria
the immediate cause of the ww1 was the assassination of archduke Ferdinand and his wife sofia, by a Serbian nationalist from Bosnia in Sarajevo. the archduke was the heir to the Austria-Hungary throne. The Austrian suspected the Serbian authority was involved and gave the Serbian an ultimatum to produce the killers. when it was not honored the declared war on Serbia, and things spilled out of control.
