Answer:
i believe it is d but it may be b
Explanation:
I think the 4th but I’m not 100% sure
<em>Hello there, and thank you for posting your question here on brainly.
What event caused World War 1?
<u>Answer:
</u>
<u>The event that caused World War 1 to start was the assassination of Archduke Franz Ferdinand on June 18th, 1914. World War 1 started a month later.
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Hope this helped you!! ♥</em>