Which one of the following categories of animals, is correctly described with no single exception in it ?

Options

A. All reptiles possess scales, have a three chambered heart and are cold blooded (poikilothermal)
B. All bony fishes have four pairs of gills and an operculum on each side
C. All sponges are marine and have collared cells
D. All mammals are viviparous and possess diaphragm for breathing

Answer

To solve the question "Which one of the following categories of animals is correctly described with no single exception in it?", we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understand the Question**: We need to identify a category of animals that is described in a way that applies to all members of that category without any exceptions.

2. **Evaluate Each Option**:
- **Option 1**: "All reptiles possess scales and have a three-chambered heart and a four-bladed."
- **Analysis**: This statement is incorrect because crocodiles, which are reptiles, have a four-chambered heart. Therefore, this option has exceptions.

- **Option 2**: "All bony fishes have 4 pairs of gills and an upper collar on each side."
- **Analysis**: This statement is correct. All bony fishes do indeed have 4 pairs of gills and an upper collar (a bony flap). There are no exceptions to this statement.

- **Option 3**: "All sponges are marine and have collar cells."
- **Analysis**: This statement is incorrect because some sponges are freshwater species. Therefore, this option has exceptions.

- **Option 4**: "All mammals are viviparous and possess a diaphragm."
- **Analysis**: This statement is incorrect because some mammals, like the platypus, are oviparous (egg-laying). Therefore, this option has exceptions.

3. **Conclusion**: After evaluating all options, the only statement that holds true for all members of the category without any exceptions is **Option 2**: "All bony fishes have 4 pairs of gills and an upper collar on each side."

### Final Answer:
The correct answer is **Option 2**: All bony fishes have 4 pairs of gills and an upper collar on each side.

---