Which sentence best supports the idea that the wall was a practical solution to the problem of who controlled Berlin, Germany?

A) When they tried to control all of Berlin, Germany, the United States and other European countries resisted.

B) They built a wall of concrete with barbed wire atop it.

C) They had soldiers with machine guns who would shoot if someone tried to climb the wall to get to freedom.

D) Mr. Gorbachev, open this gate.