The correct answer is: Remains of a medieval city.
Numaligarh Refinery Mound is a site of archaeological interest due to the possibility of finding remains of a medieval city. The mound is located in Numaligarh, Assam, India. It is a 100-meter-high (330 ft) mound that covers an area of about 100 hectares (250 acres). The mound is made up of sand, silt, and clay. It is believed to be the site of an ancient city that was destroyed by a flood.
The mound has been excavated several times since the 1950s. The excavations have revealed a number of artifacts, including pottery, coins, and jewelry. The artifacts date back to the 7th century AD. The excavations have also revealed the remains of a number of buildings, including a temple, a palace, and a market.
The Numaligarh Refinery Mound is a significant archaeological site. It is the only site in Assam that has yielded evidence of a medieval city. The site is important for understanding the history and culture of Assam.
The other options are incorrect because:
- Option (b), Harappan civilization artifacts, is incorrect because the Harappan civilization was located in the Indus Valley, which is in present-day Pakistan.
- Option (c), Ahom kingdom fortifications, is incorrect because the Ahom kingdom was located in the Brahmaputra Valley, which is in present-day Assam.
- Option (d), Buddhist monastery ruins, is incorrect because there is no evidence of Buddhist monasteries in the Numaligarh Refinery Mound.