Explanation:

Sylhet district was established on 3 January 1782, and until 1878 it was part of Bengal province. In that year, Sylhet was included in the newly created Assam Province, and it remained as part of Assam up to 1947 (except during the brief break-up of Bengal province in 1905–11). Sylhet district was divided into five subdivisions and the current Sylhet District was known as the North Sylhet subdivision. In 1947, Sylhet became a part of East Pakistan as a result of a referendum (except 3½ thanas of Karimganj subdivision) as part of Chittagong Division. It was subdivided into four districts in 1983-84 with the current Sylhet District being known as North Sylhet. It became a part of Sylhet Division after its formation in 1995.