Chondrichtyes are

Options

A. with terminal mouth
B. without operculum
C. with cycloid scales
D. with air bladder

Answer

### Step-by-Step Solution:

1. **Identify the Group**: Chondrichthyes is a class of fish that includes sharks, rays, and skates. They are characterized by having a cartilaginous skeleton.

2. **Key Characteristics of Chondrichthyes**:
- **Mouth Position**: Chondrichthyes typically have a ventral (underside) mouth, which is a distinguishing feature.
- **Operculum**: Unlike bony fish (Osteichthyes), Chondrichthyes do not possess an operculum, which is a bony flap covering the gills.
- **Scales**: They have placoid scales (not cycloid scales), which are small, tooth-like structures that give their skin a rough texture.
- **Air Bladder**: Chondrichthyes lack an air bladder, which means they must swim continuously to maintain buoyancy.

3. **Evaluate the Options**:
- **With Terminal Mouth**: This is incorrect as they have a ventral mouth.
- **Without Operculum**: This is correct, as Chondrichthyes do not have an operculum.
- **With Cycloid Scales**: This is incorrect; they have placoid scales.
- **With Air Bladder**: This is incorrect; they do not have an air bladder.

4. **Conclusion**: The correct characteristic of Chondrichthyes from the options provided is that they are "without operculum."