Answer:
Imperialism & the assasination of Archduke Franz Ferdinand.
Explanation:
One of the most significant causes of World War one was Imperialism, which is where a system where powerful nation rules and exploits one or more colonies. The assassination of the Archduke Franz Ferdinand and his wife was critical in setting off the chain of events that led to the First World War. Archduke Franz Ferdinand was heir to the throne of Austria-Hungary, and his assasination would clearly open up a bad can of worms.
