Which statement best summarizes the origins of world war ii?

a. the rise of the soviet union and the threat of international communism led countries to build up huge militaries to defend themselves from soviet aggression.
b. authoritarian leaders hoping to bring their countries glory through expansion were largely allowed to seize neighboring territories unchallenged.
c. the decision to rebuild the countries that lost during world war i allowed former military leaders to quickly regain power and reignite old tensions.
d. chaos following violent nationalist revolutions across europe and asia erupted into a series of civil wars that spread across the entire globe.