The expansion plans of the Soviets led initially to the Containment policy of the early Cold War. The United States established the Containment policy which is primary to prevent the spread of the Communism period.
The policy of containment focused on keeping communism and the Soviet Union's influence limited, rather than by trying to confront the Soviet Union directly or eliminate communism completely. It influenced US foreign policy by prompting intervention in places like Korea to stop the spread of communism.
George F. Kennan recommended the policy of containment which set the tone for US involvement in world relations following World War II. Kennan was an American diplomat in Moscow after World War II. In 1946, he sent what became known as "the long telegram" of his advice about what the USA needed to do about the Union of Soviet Socialist Republics (USSR).
People feared a direct confrontation between the USA and the USSR. Kennan advised not pushing the conflict too much, but instead just try to "contain" the Soviet Union and wait for their system to collapse under the weight of its own problems.
Several of these figures were anti-capitalist, as well as anti-religion. They were also revolutionaries, not advocates of a rigid social system so the correct answer is (4) achieving change through revolution.
