The correct answer is - c) CIA.
The United States involved itself in the biggest and most powerful collective security agreements with NATO and the UN in the period between 1945 and 1980. On the other hand, CIA can not be included as a collective organization as it is not, it is actually a security organization of one country, the United States, and it is not representing any other nation or interest.
CIA has played a crucial role on the field when it came to the political interests of the United States, and they are the ones that were managing to infiltrate, bribe, convince, propagate, and make coups and revolutions in the countries of interest of the United States. Most noticeably CIA was involved heavily in Latin America.
