The correct answer is option 4: The Russian Revolution.

In 1917, the Russian Revolution took place, which was a significant event in history. The revolution resulted in the overthrow of the Russian Tsar and the establishment of a communist government led by Vladimir Lenin. This revolution marked a major turning point in Russia`s history and had significant impacts globally, particularly in terms of the spread of communism and the reshaping of international relations. It led to the formation of the Soviet Union and had long-lasting effects on the political, social, and economic landscape of Russia and the world.

Option 1, the Battle of Trafalgar, took place in 1805, during the Napoleonic Wars. Option 2, the Battle of Waterloo, happened in 1815 and marked the end of Napoleon`s reign. Option 3, the end of World War I, occurred in 1918, a year after the Russian Revolution.