Final answer:
The collapse of the alliance system, the nationality of the assassin, and the Schlieffen Plan contributed to the outbreak of World War 1.
Step-by-step explanation:
The collapse of the alliance system, the nationality of Archduke Franz Ferdinand's assassin, and knowledge of the Schlieffen Plan can be used to investigate the reason the assassination of Archduke Franz Ferdinand sparked World War 1.
The alliance system in Europe at the time was fragile, and when the assassination happened, it led to a series of cascading events that dragged different countries into the conflict.
The nationality of the assassin, Gavrilo Princip, who was a member of a Serbian nationalist group, heightened tensions between Serbia and Austria-Hungary, ultimately leading to the outbreak of the war.
In addition, Germany's implementation of the Schlieffen Plan, which aimed to quickly defeat France and then turn east to face Russia, played a significant role in the escalation and spread of the conflict.
Learn more about reasons for the outbreak of World War 1