Explanation:

The Nawabganj Bird Sanctuary, which has been officially renamed Shaheed Chandra Shekhar Azad Bird Sanctuary, is situated in the Unnao district of Uttar Pradesh. This sanctuary is a popular destination for migratory birds and birdwatchers. Option (1) Bareilly district, (2) Badaun district, and (4) Barabanki district are other districts in Uttar Pradesh but do not host the Nawabganj Bird Sanctuary. Knowing the correct district is essential for geographical and ecological understanding of the region's protected areas. Therefore, Unnao district is the correct answer.