The policy of containment began in the late 1940s to halt the spread of communism in Europe and Asia. It became the policy of the United States for decades.

Identify the United States response to the following action below.
The Soviet Union expands into Eastern Europe following World War II.

A) Support is secured from the United Nations for economic intervention
B) League of Nations was formed
C) NATO is formed as a military defensive alliance
which letter choice is correct?