Based on your knowledge of world war 1 which event was the primary catalyst for world war 1?

The catalyst for World War 1 was the assassination of of Franz Ferdinand. Austria Hungary declared war on serbia, Russia declared war on Austria Hungary, Germany declares war on Russia, so on and so forth. Nationalism and millitary advancement together was the dynamite, the alliances were the fuses, and the assassination of Franz Ferdidand was the fire that sparked the fuze