Final answer:
The quote is associated with the concept of containment, specifically the Truman Doctrine implemented during the Cold War. The correct option is (C).
Step-by-step explanation:
The quote you provided, "It is our policy to support free peoples who are resisting Communist aggression," is associated with the concept of containment.
This policy, known as the Truman Doctrine, was implemented during the Cold War to prevent the spread of communism beyond the countries where it already existed.
The United States provided aid and military support to countries like Greece and Turkey to help them resist communist influence and maintain their freedom.