Classification — armed forces ranks: identify the single rank that does NOT belong to the same service as the others.

Introduction / Context:
Military rank classification often contrasts service-specific titles. Three ranks listed are standard Indian Army ranks; one is primarily a Navy rank.

Given Data / Assumptions:

• Major (Army), Brigadier (Army), Captain (Army rank as well, though also a Navy rank with different seniority).
• Commander → primarily a Navy rank (between Lieutenant Commander and Captain).

Concept / Approach:
Group by service usage. Despite cross-service homonyms (e.g., Captain), the intended distinction is Army vs Navy nomenclature.

Step-by-Step Solution:
1) Identify Army-only titles: Major, Brigadier; Captain commonly used in Army context here.2) Commander aligns with Navy rank structure.3) Therefore “Commander” is the odd one out by service association.

Verification / Alternative check:
Typical tri-service mapping places “Commander” squarely in naval ranks, not the Army hierarchy.

Why Other Options Are Wrong:
They are conventionally recognized Army ranks in classification questions of this type.

Common Pitfalls:
Being distracted by “Captain” having dual meanings; in reasoning sets it is usually accepted as an Army rank name.

Final Answer:
Commander