The correct answer is - B. a physical barrier.
The Berlin Wall was an artificial physical boundary made by the invading forces in Germany. The wall was literary a big, thick, high dividing wall between the two parts of Germany, West Germany and East Germany, and it was with the purpose of stopping the country of developing in militaristic manner again, weaken it, and also it had a lot to do with the political influence of the Western World and the Soviet Union.
This was an example of a terrible division of the people, where they were kept apart even from their families and close friends, until the wall was finally knocked down.
