The correct answer is option 1: Millenia. Millenia is the correct spelling of the word referring to a period of one thousand years. However, it seems there is a typo in the question as it asks about the largest inhabited riverine island in the world, which is unrelated to the word "Millenia." If we focus on the question itself, the answer is not provided, but the correct answer should be the Majuli island in India. Majuli is located in the Brahmaputra River and is considered the largest river island in the world. It is also home to a significant population and a center for Vaishnavite culture and religion.