In which of the following groups of vertebrates is parental care mostly exhibited?

Analyze the question: You are asked which vertebrate group shows parental care the most. Parental care means looking after eggs or young: feeding, protecting, and teaching them.

Explain the concept: Parental care varies across vertebrate classes:

• Amphibia (C): Most abandon their eggs after laying them in water. Care is minimal and found in only a few species.
• Reptilia (B): Most bury their eggs and leave. A few, like crocodiles, guard their nests, but this is not typical.
• Aves (A): Birds show a lot of care. They build nests, incubate eggs, and feed the chicks. Parental care is well developed here.
• Mammalia (D): Mammals show the highest level of care. The young develop inside the mother (in most), are nourished by milk from mammary glands, and are protected, groomed, and taught for a long time after birth.

Solution: Both birds and mammals care for their young, but only mammals combine all of these features:

1. Internal development of the young (viviparity, in most)
2. Suckling with milk
3. A long period of dependence on the parents
4. Learning and training of the young

So "mostly exhibited" points to Mammalia.

Answer: D. Mammalia

Exam tip: When a question asks which group shows the most parental care, think "mammals = mammary glands = milk = long care". Remember the ladder of care: Amphibia (least) → Reptilia → Aves → Mammalia (most).