The Paris Peace Conference would work better for 1919. The Treaty of Versailles only applied to Germany among the Central Powers. There was other many other treaties signed between 1918 and 1920 (Trianon, Sèvres, Neuilly,...) and some conflicts directly linked to WW1 were actually ended by other treaties way later (Treaty of Lausanne for the Ottomans, for example). It would be as relevant to use any of these treaties than the Versailles one. There was several belligerents on both sides and the only thing that encompasses all of them is the Paris Peace Conference... but yeah, that's not a treaty.
Good quiz, otherwise!