A sapling is a young tree (age/young-one relation). By the same relation, a young horse is called what?

Introduction / Context:
This is a classic young-one analogy. “Tree → sapling” encodes the juvenile stage of the organism. We must supply the standard juvenile term for a horse. The correct zoological label is “foal”.

Given Data / Assumptions:
We use common English terms for young animals and standard breed/sex distinctions only when needed.

Concept / Approach:
Preserve “species → juvenile term”. “Foal” is the young of a horse (male foal = colt; female foal = filly). Avoid confusing size/breed (pony) or hybrids (mule) with age terms; “cub” belongs to felids/ursids; “stag” is an adult male deer.

Step-by-Step Solution:

Verification / Alternative check:
Dictionaries and basic zoology lists confirm “foal” as the generic young horse.

Why Other Options Are Wrong:
Pony: small breed/adult possible; Mule: hybrid of horse and donkey; Cub: wrong taxon; Stag: adult deer.

Common Pitfalls:
Equating “pony” with “young horse”; it is not primarily an age term.

Final Answer:
Foal