The correct answer is D. The United States failed to join the newly created League of Nations after World War I ended.
The League of Nations was based on the principles of international cooperation, arbitration of conflicts and collective security. The Covenant of the League of Nations was drafted at the first sessions of the Paris Conference, which began on January 18, 1919, by initiative of the President of the United States, Woodrow Wilson.
The United States never joined the League, due to the refusal of the US Congress to participate in it, even though it belonged to its affiliated organizations.