A.to make the United States gain time to arm itself
B.to actually help the aggressors by making clear that the United States would not intervene
C.to get the United States involved in the war
D.to prevent the United States form being dragged into the war

A.The main cause was big power struggle for control of the world.
B.It was the worldwide economic crisis.
C.It was the military expansion of Japan,and Germany.