Explanation:

Let’s quickly go over the options:

- G.S. Ghurye: Known as the “father of Indian sociology,” he wrote about caste, tribes, and civilization, but his primary focus was not on regional dimensions.

- N.K. Bose: Famous for his work on Indian society and culture, especially tribal and urban studies, but not specifically on regionalism.

- Radhakamal Mukherjee: Extensively discussed regional dimensions in India through his studies on regional planning, ecology, and rural-urban systems.

- S.C. Dube: Focused more on Indian villages and modernization rather than explicit regional dimensions.

Correct Answer: Option 3 – Radhakamal Mukherjee