All chordates possess

Options

A. exoskeleton
B. limbs
C. skull
D. axial skeletal rod of notochord

Explanation

**Step-by-Step Solution:**

1. **Understanding Chordates**: Chordates are a diverse group of animals that belong to the phylum Chordata. They are characterized by certain features that distinguish them from other animal groups.

2. **Identifying Key Features**: All chordates possess four key features at some stage of their life cycle:
- A notochord
- A dorsal hollow nerve cord
- Pharyngeal slits or clefts
- A post-anal tail

3. **Focusing on the Notochord**: The notochord is a flexible, rod-like structure that provides support. It is present in all chordates during some stage of their development. In many vertebrates, the notochord is replaced by the vertebral column (backbone) during development.

4. **Excluding Other Options**:
- Not all chordates have an exoskeleton (this is more common in arthropods).
- Not all chordates possess limbs (some, like fish, have fins instead).
- Not all chordates have a skull (for example, some primitive chordates like tunicates do not).

5. **Conclusion**: The correct answer to the question "All chordates possess" is the notochord, which is a defining characteristic of the phylum Chordata.

**Final Answer**: All chordates possess a notochord.

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