The correct answer is: Coastal plains.
Tribal populations in Goa are largely concentrated in the coastal plains. This is because the coastal plains are more fertile and have a more temperate climate than the hilly regions. The coastal plains are also more accessible to markets and other resources, which makes it easier for tribal people to earn a living.
The hilly regions of Goa are less populated by tribal people because they are more difficult to access and have a less hospitable climate. The hilly regions are also more sparsely populated overall, which means that there are fewer resources available to tribal people.
The urban areas of Goa are also less populated by tribal people. This is because urban areas are more expensive to live in and tribal people often have difficulty finding jobs in the formal economy. Tribal people who live in urban areas often live in slums or other informal settlements.
Overall, tribal populations in Goa are largely concentrated in the coastal plains. This is because the coastal plains are more fertile, have a more temperate climate, and are more accessible to markets and other resources.