"Mr. Gorbachev, tear down this wall!" To what does this famous line reference?

a
John F. Kennedy was advocating the end of the Berlin Crisis through the symbol of the Iron Curtain.
b
Ronald Reagan was advocating of the end of the Cold War through the symbol of the Berlin Wall.
c
George Bush was advocating the end of the Gulf War through the symbol of the Kuwait Border Wall.
d
Jimmy Carter was advocating the end of the Israeli - Palestine Conflict through the symbol of the West Bank Wall.