Classification (role–collective/place): Three pairs show a person as a member of a group or housed in a place; one pair shows the person who heads an institution. Identify the odd pair.

Introduction / Context:
Lexical relation classification often distinguishes membership relations from leadership relations. In this question, three options specify a person as a member of a group or a resident of a place, whereas one option specifies a person who acts as the head of an institution. The latter is not membership but governance, which creates the exception.

Given Data / Assumptions:

• Pairs: Principal : School, Soldier : Barrack, Artist : Troupe, Singer : Chorus.
• Membership or location relations: artist belongs to a troupe, singer belongs to a chorus, soldier resides in or is stationed at a barrack.
• Headship relation: a principal is the person in charge of a school, responsible for leadership and administration.

Concept / Approach:
Identify whether the left term is a member contained in the right term or a leader who oversees the right term. Membership and residence indicate inclusion, while headship indicates control or governance. The mismatch between inclusion and control marks the odd pair.

Step-by-Step Solution:

Verification / Alternative check:
Rephrase as “X is in Y.” Artist is in a troupe, singer is in a chorus, soldier is in a barrack. “Principal is in a school” may be literally true, but the defining relation is leadership rather than membership. The functional role differs from the other three.

Why Other Options Are Wrong:

Common Pitfalls:
Focusing on physical co location rather than the type of relation. Leadership versus membership is the key distinction here.

Final Answer:
Principal : School