The correct answer is: d) Srikakulam.
Srikakulam district has the highest concentration of Scheduled Tribe population in Andhra Pradesh. According to the 2011 census, the Scheduled Tribe population in Srikakulam district is 27.4%, which is higher than the state average of 6.9%. The main Scheduled Tribes in Srikakulam district are the Koyas, Kondhs, and Saora.
Visakhapatnam district has a Scheduled Tribe population of 16.8%, East Godavari district has a Scheduled Tribe population of 13.3%, and Kurnool district has a Scheduled Tribe population of 10.4%.
The Scheduled Tribes are a group of indigenous peoples who are officially recognized by the Indian government. They are entitled to certain benefits and protections under the Indian Constitution.