Classification (hyponymy vs co-hyponyms): Three pairs are coordinate/similar-level items; one pair is a subtype–supertype relation. Identify the odd pair.

Introduction / Context:
Lexical relations include co-hyponymy (sibling categories at the same level) and hyponymy (subtype–supertype). In this set, most pairs juxtapose terms that are roughly on the same level or related by association. One pair is a clear subtype–supertype: a pistol is a kind of gun.

Given Data / Assumptions:

• Pond and lake: coordinate water bodies (size/depth distinctions).
• Car and bus: coordinate vehicle types (different capacities/uses).
• Church and monument: associated terms; a church may be a monument but not by definition; relation is not clean hyponymy.
• Pistol and gun: pistol is a type of gun (hyponym→hypernym).

Concept / Approach:
Identify which pair expresses a direct “is-a” relation. That pair is the odd one because the others are coordinate or loosely associated, not subtype–supertype.

Step-by-Step Solution:

Verification / Alternative check:
Attempt reversing: “Gun is a kind of pistol” (false), confirming directionality and proper hyponymy only in this pair.

Why Other Options Are Wrong:

Common Pitfalls:
Overinterpreting church : monument as hyponymy; many churches are not monuments, and many monuments are not churches.

Final Answer:
Pistol : Gun