27.) which was a cause of world war i? a.) political revolutions in europe left nations unstable b.) europe's system of military alliances enlarged small conflicts c.) russia's race to industrialize threatened the economy of other european countries. d.) the second industrial revolution led to international rivalries. 28.) which countries formed an alliance that would lead to world war i? a.) russia and austria-hungary b.) serbia and russia c.) austria-hungary and france d.) britain and germany