The Narendra Mandal or Chamber of Princes was inaugurated in 1921 by the Duke of Cannaught. This was a political body that represented the princely states of British India. It provided a platform for the princely states to discuss and negotiate with the British government on matters of governance and administration. Option 1, Lord Curzon, was the Viceroy of India from 1899 to 1905 and was not involved in the inauguration of the Chamber of Princes in 1921. Option 2, Lord Wellesley, was the Governor-General of India from 1798 to 1805 and was not associated with the Chamber of Princes. Option 4, Duke of Wellington, was a British military leader and politician and had no connection to the chamber. Therefore, the correct answer is option 3, the Duke of Cannaught.