Which of the following is not a characteristic of class chondrichthyes?

Options

A. Gill'slits are separate and without operculum
B. They are predaceous
C. Airbladder is present
D. Notochord is persistent throughout the life

Answer

To determine which characteristic is not associated with the class Chondrichthyes, we can analyze the known features of this class and compare them with the options provided.

### Step-by-Step Solution:

1. **Understand the Class Chondrichthyes**:
- Chondrichthyes includes cartilaginous fishes such as sharks, rays, and skates. Their skeletons are primarily made of cartilage rather than bone.

2. **Identify Key Characteristics of Chondrichthyes**:
- Cartilaginous skeleton: Unlike bony fish, Chondrichthyes have a skeleton made of cartilage.
- Gills: They have multiple gill slits, typically five to seven, which are not covered by an operculum (a bony flap).
- No swim bladder: Chondrichthyes do not possess a swim bladder, which is an air-filled organ that helps in buoyancy. Instead, they rely on their large livers filled with oil for buoyancy.
- Predatory behavior: Many members of this class are predatory and have adaptations for hunting.

3. **Analyze the Options**:
- If one of the options mentions the presence of a swim bladder, that would be the characteristic not found in Chondrichthyes, as they do not have this feature.
- Other options may include features like gills or cartilaginous skeleton, which are indeed characteristics of Chondrichthyes.

4. **Conclusion**:
- The characteristic that is not found in Chondrichthyes is the presence of a swim bladder.

### Final Answer:
The characteristic that is not associated with class Chondrichthyes is the presence of a swim bladder.

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