Among the Factors That Led to World War II Was

Among the factors that led to World War II was

A) the return of the United States to its traditional isolationism after World War I.
B) the failure of Britain and France to strongly oppose flagrant German violations of the Versailles treaty.
C) the inability of the small, weak successor states to Austria-Hungary to oppose Germany.
D) the failure of efforts of collective security such as the League of Nations and treaties.
E) all of the above.