Explanation:

- F.G. Bailey (Option 2) is the scholar who emphasized defining tribe and caste in terms of a continuum, with tribes at one end and castes at the other.

- David Mandelbaum (Option 1) contributed majorly to studies on Indian society but did not specifically focus on the tribe-caste continuum.

- N.K. Bose (Option 3) was noted for work on tribal societies but not specifically this concept of continuum.

- M.N. Srinivas (Option 4) is well-known for concepts like “Sanskritization” and “dominant caste” rather than the tribe-caste continuum.

- The idea is that there isn’t a strict boundary between tribe and caste; rather, they can blend gradually across a spectrum.

Correct Answer: Option 2, F.G. Bailey.