The correct answer is B) It created a buffer zone to protect it from invasion.
The reason that the Soviet Union gave for its expansion after World War II was that "it created a buffer zone to protect it from invasion."
Soviet leaders needed to protect their western borders from future attacks. That is why this buffer zone was necessary to them. But the USSR also used these territories to spread Communism and exert control over them. We are talking about Poland, East Germany, Czechoslovakia, Hungary, and Romania.