The event that happened first and led to the other three is C: World War I.
World War I set the stage for the Bolshevik Revolution (A), as the war created significant social and political unrest in Russia. The end of World War I also led to the Treaty of Versailles (B), which was signed in 1919 to formally end the conflict. Additionally, the aftermath of the war contributed to various political movements in Europe, including the rise of Fascism in Italy (D).