Wann wurde die österreichische Bundesverfassung beschlossen?

Why this is the correct answer

Austria's Federal Constitution was adopted on 1 October 1920, making it one of the earliest written constitutions in the world still in force today. It was drafted primarily by the legal scholar Hans Kelsen and established Austria as a democratic federal republic. After being suspended during the authoritarian Ständestaat and Nazi periods, it was reinstated in 1945.