Which one of the following is not an island of the Sundarban region?

Correct answer: Sabujdwip

Explanation: The correct answer is D. Sabujdwip. The Sundarbans region in South 24 Parganas district of West Bengal is home to several inhabited and uninhabited islands, such as Gosaba, Patharpratima, and Jambudwip, all of which are located within or near the mangrove delta. Gosaba is the last inhabited island of the Sundarbans and an important administrative block. Patharpratima is a major island block with dense population and agricultural activities. Jambudwip, although uninhabited, lies off the coast and is part of the deltaic ecosystem influenced by the Bay of Bengal. However, Sabujdwip is not part of the Sundarbans delta. It is located near Katwa in Purba Bardhaman district, on the Ajay River, far from the delta region.