The correct answer is: a) Hilly and forested regions.
Tribal communities in Andhra Pradesh are primarily concentrated in hilly and forested regions. This is because these regions provide them with the resources they need to survive, such as food, water, and shelter. Additionally, these regions are often less populated than other areas, which gives tribal communities more space to live and practice their traditional way of life.
Option b) Coastal areas is incorrect because tribal communities are not as concentrated in coastal areas as they are in hilly and forested regions. This is because coastal areas are often more developed than other areas, which can make it difficult for tribal communities to maintain their traditional way of life.
Option c) Urban centers is incorrect because tribal communities are not as concentrated in urban centers as they are in hilly and forested regions. This is because urban centers are often more expensive to live in than other areas, which can make it difficult for tribal communities to afford to live there.
Option d) Fertile plains is incorrect because tribal communities are not as concentrated in fertile plains as they are in hilly and forested regions. This is because fertile plains are often more populated than other areas, which can make it difficult for tribal communities to maintain their traditional way of life.