Option 1 -> Andaman and Nicobar are oceanic island groups in the Bay of Bengal, not river islands.
Option 2 -> Majuli is a river island in the Brahmaputra River, Assam, India, and is recognized as the world's largest river island.
Option 3 -> Lakshadweep is an archipelago of coral islands in the Arabian Sea, not a river island.
Option 4 -> Indus is a river itself, not an island.
Hence, Option 2: Majuli Island -> Majuli, located in the Brahmaputra River in Assam, India, holds the distinction of being the world's largest river island with an area of approximately 352 square kilometers (though it has been shrinking due to erosion) -> correct