Answer :
D.United States
The US refused to join the League of Nations because of a philosophy that had long existed in America that is known as "Isolationism". The concept of Isolationism gradually evolved from the beginnings of the United States of America.
The US refused to join the League of Nations because of a philosophy that had long existed in America that is known as "Isolationism". The concept of Isolationism gradually evolved from the beginnings of the United States of America.