The correct answer is option 4, 1971. Bangladesh gained independence from Pakistan in 1971 after a nine-month long war of liberation. Prior to this, Bangladesh was known as East Pakistan and was part of Pakistan since the partition of British India in 1947. The creation of Bangladesh marked the end of a struggle for self-determination and the establishment of a sovereign nation for the Bengali-speaking population of East Pakistan. The year 1971 is significant in the history of Bangladesh as it marks the emergence of the country as an independent nation.