What event ended World War I?

The event that ended World War I was the signing of the Treaty of Versailles. Signed on June 28, 1919, the treaty was a formal agreement between the Allied powers and Germany that officially concluded the hostilities of the war, which lasted from 1914 to 1918. The Treaty outlined the reparations Germany was to pay, territorial adjustments, and limitations on the size of the German military, among other issues, and played a significant role in reshaping the international landscape in the aftermath of the war.

The other options refer to significant events in different historical contexts. The fall of Berlin occurred during World War II, marking the end of Nazi Germany. The bombing of Hiroshima was a pivotal moment during World War II, leading to Japan's surrender. The invasion of Poland marked the beginning of World War II, not its conclusion. Each of these events, while crucial in their respective conflicts, did not pertain to the ending of World War I.