Final answer:
The Russian Revolution was not a cause of World War I but occurred during the war, leading to Russia's withdrawal. The main causes of the war are represented by the acronym MAIN: Militarism, Alliances, Imperialism, and Nationalism.
Step-by-step explanation:
When analyzing the main causes of World War I, the correct option that does not belong is the Russian Revolution. The MAIN acronym simplifies the long-term causes of the war as Militarism, Alliances, Imperialism, and Nationalism. While the Russian Revolution occurred during the war and was a significant event, it was not one of the factors that led to the beginning of World War I, which started in 1914. Rather, it contributed to the eventual withdrawal of Russia from the war in 1917. On the other hand, the other causes listed - Imperialism, the building of large armies (part of Militarism), and Nationalism - are well-recognized as key factors that set the stage for one of the deadliest conflicts in history. Imperialism led to a competitive environment among European powers, which culminated in the division of Africa at the Berlin Conference. Militarism saw the great powers of Europe amass large armies in a show of strength and preparedness. Lastly, intense Nationalism fostered an environment where nations were willing to aggressively defend and promote their interests, often at the expense of others.