The nye committee hearings in the 1930s popularized the idea that a key factor leading the united states into world war i had been

a. german aggression.
b. the power vacuum caused by the decline of the ottoman turkish empire.
c. the need to protect american bank loans to the allies (which were used to buy arms from u. s. manufacturers).
d. the need to protect american overseas colonial possessions (which were threatened by german and japanese expansion).