Geometric designs and motifs representing natural elements are commonly found in the traditional wall paintings of the:

Apatani tribe
Nyishi tribe
Wancho tribe
Idu Mishmi tribe

The correct answer is: a) Apatani tribe.

The Apatani tribe is a major tribe in the Indian state of Arunachal Pradesh. They are known for their unique culture and traditions, including their traditional wall paintings. These paintings are often geometric in design and feature motifs representing natural elements such as the sun, moon, stars, and animals. The paintings are believed to have both religious and decorative purposes.

The Nyishi tribe is another major tribe in Arunachal Pradesh. They are known for their colorful traditional dress and their elaborate festivals. The Nyishi do not have a tradition of wall painting.

The Wancho tribe is a tribe found in the eastern part of Arunachal Pradesh. They are known for their warrior culture and their intricate woodcarvings. The Wancho do not have a tradition of wall painting.

The Idu Mishmi tribe is a tribe found in the northern part of Arunachal Pradesh. They are known for their unique language and their traditional dress. The Idu Mishmi do not have a tradition of wall painting.

In conclusion, the correct answer is: a) Apatani tribe. The Apatani tribe is a major tribe in the Indian state of Arunachal Pradesh. They are known for their unique culture and traditions, including their traditional wall paintings. These paintings are often geometric in design and feature motifs representing natural elements such as the sun, moon, stars, and animals. The paintings are believed to have both religious and decorative purposes.