To complete the sentence correctly, use 'would not have taken.' This implies that the assassination of Archduke Franz Ferdinand was crucial in leading to World War I. The sentence articulates a hypothetical historical scenario. ;
The appropriate completion is 'would not have taken', indicating that the assassination of Archduke Franz Ferdinand was a key factor in triggering World War I. This choice reflects a hypothetical situation regarding the significance of this historical event. The complete sentence is: 'Some historians argue that if a Serbian nationalist had not assassinated Archduke Franz Ferdinand in 1914, World War I would not have taken place.'
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