The correct answer is: c) Prehistoric settlements.
The Dibang Valley is a remote region in the Indian state of Arunachal Pradesh. It is home to a number of indigenous tribes, and is thought to have been inhabited for thousands of years. Archaeological surveys have uncovered evidence of prehistoric settlements in the region, including stone tools, pottery, and human remains.
The Ahom kingdom was a powerful kingdom that ruled over much of northeastern India from the 13th to the 18th centuries. The Ahoms were originally from Tibet, and their arrival in the Dibang Valley is thought to have led to the displacement of some of the indigenous tribes. However, there is no evidence that the Ahoms established any permanent settlements in the region.
Tibetan Buddhist influence is also evident in the Dibang Valley, but it is thought to have been limited to trade and cultural exchange. There is no evidence that Tibetan Buddhists ever established any permanent settlements in the region.
Trade links with Southeast Asia are also thought to have existed in the Dibang Valley, but they were also limited to trade and cultural exchange. There is no evidence that Southeast Asian traders ever established any permanent settlements in the region.
Therefore, the correct answer is: c) Prehistoric settlements.