Which of the following has a cartilaginous endoskeleton

Options

A. Elasmobranch
B. Dipnoi
C. Mollusca
D. Bony fishes

Explanation

To determine which of the following has a cartilaginous endoskeleton, we will analyze each option provided: elasmobranch, dipnoi, mollusca, and bony fish.

### Step-by-Step Solution:

1. **Understanding Endoskeleton**:
- An endoskeleton is an internal skeleton that provides support to the body of an organism. It can be made of cartilage or bone.

2. **Analyzing the Options**:
- **Elasmobranch**: This group includes sharks and rays. They belong to the class Chondrichthyes, which is characterized by having a cartilaginous endoskeleton.
- **Dipnoi**: This group refers to lungfish, which belong to the class Osteichthyes. They have a bony endoskeleton, not cartilaginous.
- **Mollusca**: This phylum includes organisms like snails and clams. They have an exoskeleton (shell) made primarily of calcium carbonate, not an endoskeleton made of cartilage.
- **Bony Fish**: As the name suggests, bony fish have an endoskeleton made of bone, not cartilage.

3. **Conclusion**:
- The only option that has a cartilaginous endoskeleton is **Elasmobranch**.

### Final Answer:
- The correct answer is **Elasmobranch**.