The Iron Curtain served as an imaginary boundary between the Soviet Union and the West world. The term iron curtain was used by the Prime Minister Winston Chruchill in his speech and popularised thereafter.
This boundary divided the communist eastern Europe from the west. Stalin build barbed wires, ditches, and concrete walls to stop his citizen from fleeing to the Western Europe.
Therefore, the Iron Curtain served as a buffer between the Soviet Union and the West. Thus option C is correct.
