The correct statement is "an alliance aimed at preventing the spread of communism."
During the time in which this organization was formed, 1955, communism was spreading throughout several different nations in the Eastern hemisphere. The goal in making this organization was to ensure that this did not happen to any of the member nations. This organization was also unique in the sense that it included countries who were not located in Southeast Asia. Some of the original members include the United States, Australia, New Zealand, the Philippines, and Thailand.