Base your answer to the next question on the passage below. "...The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defense...will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the...area..."
Which of the following developments was most directly a response to the agreement in this passage?
A. creation of the United Nations
B. establishment of the Warsaw Pact
C. terrorist attacks of September 11, 2001
D. German invasion of Czechoslovakia and Poland