Which of the following languages is most closely related to Old Norse?

Old Norse was a North Germanic language that was spoken by inhabitants of Scandinavia and their overseas settlements from about the 9th to the 13th centuries.

The modern descendants of the Old West Norse dialect are the West Scandinavian languages of Icelandic, Faroese, Norwegian and the extinct Norn language of Orkney and Shetland; the descendants of the Old East Norse dialect are the East Scandinavian languages of Danish and Swedish. Norwegian is descended from Old West Norse, but over the centuries it has been heavily influenced by East Norse, particularly during the Denmark–Norway union.

Among these, the grammar of Icelandic and the Faroese have changed the least from Old Norse in the last thousand years.