Primary causes of world war one?

The real causes of World War I included politics, secret alliances, imperialism, and nationalistic pride. However, there was one single event, the assassination of Archduke Ferdinand of Austria, which started a chain of events leading to war.

Explanation:

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i beleive a. is the only possible answer

ba geologist finds four sedimentary rock she determines that no geologic events have shifted the layers she labeles them a,b,c,dbfrom top to bottom