Why did the United States of America join World War 1?

Question

a) Partly to retaliate the repeated German attacks on American vessels.
b) Partly to provide moral support to its allies, namely France and Great Britain.
c) Partly to protect its colonies all around the world.
d) Partly to fight communism in Europe.

Answer 1

a) Partly to retaliate the repeated German attacks on American vessels.
b) Partly to provide moral support to its allies, namely France and Great Britain.