SEATO refers to:-

South East Asian Treaty Organisation

The correct answer is Option (4) - South East Asian Treaty Organisation

During the Cold War period, in East and Southeast Asia and in West Asia (Middle East), the United States built an alliance system called — The Southeast Asian Treaty Organisation (SEATO) and the Central Treaty Organisation (CENTO).
SEATO (Southeast Asia Treaty Organization) became inactive in 1977. SEATO was a collective defence organization formed in 1954 to counter the spread of communism in Southeast Asia. However, it lost its relevance over time, and the organization officially dissolved in 1977.