What limits do skeletons on American civilizations pre-1600 have as historical sources?

What caused the united states to side with britain during world war i?

Supporters of using the atomic bomb at the end of world war ii believed that a japan might win the war if the bomb was not used. b americans were tired of war and the us should end it quickly. c russia was developing a bomb and the us needed to use it first. d japan was developing a bomb and the us needed to use it first.

Who was the leader of the black nationalists in the 1920s?