Category of animals with correct description:

a) All bony fishes have four pairs of gills and an operculum on each side.

Explanation:

Bony fishes are a diverse group of aquatic animals, which include more than 28,000 species. They have a bony skeleton, swim bladder, and scales. The following points explain why the given statement is true for all bony fishes without any exception:

- Four pairs of gills: Bony fishes have gills for respiration, which extract oxygen from water. They have four gill arches on each side, and each arch has a pair of gills. Therefore, bony fishes have four pairs of gills in total.

- Operculum: Bony fishes have a bony flap called operculum on each side of their head, which covers and protects the gills. This flap helps in pumping water over the gills for respiration. Therefore, bony fishes have an operculum on each side.

- No exception: There is no known species of bony fish that does not have four pairs of gills and an operculum on each side. Hence, the given statement is correct with no single exception.

Other options and their explanation:

b) All mammals are viviparous and possess diaphragm for breathing.

- Viviparous: Mammals are a group of animals that give birth to live young, which develop inside the mother's body through a placenta. However, there are a few exceptions, such as monotremes (egg-laying mammals) and marsupials (pouched mammals) that are not viviparous.

- Diaphragm: The diaphragm is a dome-shaped muscle that separates the chest cavity from the abdominal cavity and plays a crucial role in breathing. However, there are a few mammals, such as monotremes and marsupials, that do not have a diaphragm.

- Exception: Therefore, the given statement is not true for all mammals, as there are exceptions to both characteristics (viviparity and diaphragm).

c) All sponges are marine and have collared cells.

- Marine: Sponges are aquatic animals that live in both marine and freshwater environments. Therefore, the given statement is not true for all sponges.

- Collared cells: Sponges have specialized cells called choanocytes or collared cells, which have a collar-like structure that helps in capturing food particles. Therefore, the second part of the statement is true for all sponges.

- Exception: However, there are a few species of sponges that do not have collared cells, such as some members of the class Demospongiae. Therefore, the given statement is not true for all sponges.

d) All reptiles possess scales, have a three-chambered heart, and are cold-blooded (poikilothermal).

- Scales: Reptiles are a group of animals that have dry, scaly skin, which protects them from desiccation and predators. Therefore, the given statement is true for all reptiles.

- Three-chambered heart: Reptiles have a three-chambered heart, which consists of two atria and one ventricle. However, there are a few exceptions, such as crocodilians, which have a four-chambered heart. Therefore, the given statement is not true

Option b me platypus is oviparous so this is wrong option c me spngilla are fresh water sponge so wrong option d me crocodile is exception so a option is correct