Overall, the interwar period is defined by these political and economic factors clearing the path for World War II: • the failure of the Treaty of Versailles, which was seen as unjust and humiliating by the Germans; • the Great Depression, which challenged the world economic order and pushed nation states to self-sufficiency and protectionism; • the rise of Hitler and his revisionist policies; • the unsuccessful French and British appeasement policy towards aggressors; and • the failure of the League of Nations and the concept of collective security. The correct answer is D.