Option 1: Bangladesh -> Mukti Bahini was the guerrilla resistance force that fought against the Pakistani military during the 1971 Bangladesh Liberation War.
Option 2: Sri Lanka -> Mukti Bahini had no role in Sri Lanka's history or conflicts.
Option 3: Vietnam -> Vietnam had its own independence movements and guerrilla forces, not Mukti Bahini.
Option 4: Nepal -> Mukti Bahini was not involved in Nepal's political history.
Hence, Option 1: Bangladesh -> The Mukti Bahini (meaning "Liberation Force") was formed in 1971 by Bengali military defectors, paramilitary personnel, and civilians to fight against the Pakistani military occupation during the Bangladesh Liberation War. With support from India, they played a crucial role in liberating East Pakistan, which became the independent nation of Bangladesh in December 1971. -> correct