Answer:
The four tribal groups in Arunachal Pradesh;
1. The Adi tribal group
The Adi are subsistence farmers who live in the foothills of the Himalayas in the far north of India.The majority of the Adi people believe in Donyi-Polo which is the designation given to the indigenous religion of animistic and shamanic type. They wear helmets carved out of deer and bearskins and canes. The Adi are considered as Scheduled Castes.
2.The Nyishi tribal group
Nyishi meaning 'the land of the people'. The Nyishi tribe is also called Bangni and Dafla, there are found in the Eastern Bhutan and Arunachal Pradesh. They speak a Tibeto-Burman language of the Sino- Tibetan family. They practice what can be called almost pagan or pre- Aryan beliefs which is quite evident from their worship of trees, rocks, and plants amongst other things. Like other tribes they too sacrifice animals to please spirits and deities. The men wear cotton sleeveless shirts with the mantle of cotton locked around the throat and shoulders. They normally tie their hair with a Tibetan thread. The women drape a cotton mantle around the body and tie one portion at right shoulder and keep open the left shoulder.