Concept:
This question is based on classification of animal terms.
Step 1: Analyze each option.
Joey → baby of a kangaroo
Fawn → baby of a deer
Foal → baby of a horse
Hen → adult female bird
Step 2: Identify the difference.
Joey, Fawn, and Foal are all young ones (babies) of animals.
Hen is an adult animal, not a young one.
Hence, Hen is the odd one out.