Step 1: Conceptual Understanding: The query requires the identification of the fundamental attributes of India's traditional caste system, as delineated in sociological discourse by scholars such as G.S. Ghurye.
Step 2: Detailed Analysis:
(A) Caste is an ascribed status: Verified. An individual's caste is determined by birth and is immutable.
(B) Caste groups are 'endogamous': Verified. Endogamy mandates marriage exclusively within one's designated caste.
(C) Caste is an achieved status: Discredited. Achieved status is acquired through merit or selection (e.g., profession). Caste is its antithesis, being ascribed.
(D) Castes involve segmental organization: Verified. The caste system stratifies society into discrete, hereditary segments, each with specific customs, regulations, and hierarchical standing.
(E) Caste groups are based on choice of individuals: Discredited. Membership in a caste is dictated by birth, not by personal volition.
Consequently, the valid characteristics are (A), (B), and (D).
Step 3: Conclusive Answer: The definitive set of characteristics defining the caste system comprises (A) Ascribed status, (B) Endogamy, and (D) Segmental organization.