Final answer:
Eastern European countries were separated from the rest of the world following World War II by being occupied and controlled by the Soviet army.
Step-by-step explanation:
The correct answer is: It was occupied and controlled by the Soviet army. Following World War II, Eastern European countries were separated from the rest of the world by being under the control of the Soviet Union. The Soviet army occupied and established communist regimes in these countries, effectively isolating them from the rest of the world. This separation lasted for several decades until the dissolution of the Soviet Union in 1991.
Learn more about Soviet control of Eastern Europe