1. why is “the balkan powder keg explodes” an apt title for a discussion of the causes of world war i? a. overpopulation inclined the region toward expansion through warfare. b. diverse trade relations involved the region in external wars. c. differences in wealth caused revolutionary movements. d. ethnic tensions made the 2. which specific event caused the united states to enter world war ii? a. the rise of hitler to power in germany b. the attack on the navy base at pearl harbor c. the use of navy warfare against civilian ships d. the conquering of nations in europe and asia 3. which technologies and conditions made world war i a new kind of war? select all that apply. a. heavy naval combat b. trench warfare c. poison gas d. field hospitals and medics e. rapid-fire machine guns f. gunpowder and cannons 4. which justification did u. s. officials give for sending t