Final answer:
The outbreak of World War I was mainly caused by nationalism and the assassination of Archduke Franz Ferdinand. The Industrial Revolution was not a direct trigger for the war but contributed to the way it was fought.
Step-by-step explanation:
Nationalism and the assassination of Archduke Franz Ferdinand were both key factors that led to the outbreak of World War I. However, the Industrial Revolution was not a direct cause of the war. Instead, it was one of the contributing factors that changed the dynamics of warfare during the conflict.
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