Question

Which event triggered the start of World War I in Europe?

Answer 1

the assassination of Archduke Francis Ferdinand in Sarajevo.

Step-by-step explanation:

sample answer

Answer 2

The assassination of Archduke Franz Ferdinand caused a war between Hungary- Austria and Serbia. Many countries joined in because of the treaty alliance system; it was a bit like a chain reaction. WWI was declared on July 28, 1914.
Hope that answered your question.