All adult vertebrates possess

Options

A. Renal portal system
B. Pharyngeal gill slits
C. Ventral four-chambered heart
D. Dorsal hollow central nervous system

Answer

### Step-by-Step Solution

1. **Identify the Phylum and Subphylum**:
- All adult vertebrates belong to the phylum Chordata and the subphylum Vertebrata.

2. **Key Characteristics of Adult Vertebrates**:
- The main structures that define adult vertebrates include:
- **Vertebral Column**: This is the backbone, which is a defining feature of vertebrates.
- **Nerve Cord**: Specifically, a dorsal hollow nerve cord, which develops into the spinal cord and brain.
- **Cranium**: The brain is encased in a protective structure known as the cranium.

3. **Excretory System**:
- Most adult vertebrates possess a renal portal system that functions as an excretory organ, except for some primitive forms like hagfish and lampreys.

4. **Respiratory Structures**:
- Pharyngeal gill slits are present in the embryonic stage of all chordates but may not be retained in all adult vertebrates.

5. **Circulatory System**:
- Not all vertebrates have a four-chambered heart; this feature is specific to mammals. Other vertebrates may have different heart structures.

6. **Conclusion**:
- The most universal characteristic of all adult vertebrates is the **dorsal hollow central nervous system**, which includes the spinal cord and brain.

### Final Answer:
All adult vertebrates possess a **dorsal hollow central nervous system**.

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