How was Stalin able to gain control of Eastern Europe by 1948? Select all that apply.
a. Eastern European countries freely voted for communism because the Soviets had liberated them from the Nazis.
b. Stalin established people's republics which were puppets of the Soviet Union.
c. Elections were staged and political opponents were arrested.
d. The Soviet army, left in place after the war, pressured and scared local citizens into submitting to Communist rule.