A common characteristic of all vertebrates is

Options

A. Presence of skull
B. Division of body into head, neck trunk and tail
C. Presence of two pairs of functional appendages
D. Body is covered with an exoskeleton

Explanation

**Step-by-Step Solution:**

1. **Understanding Vertebrates**: Vertebrates belong to the phylum Chordata. They are characterized by having a backbone or spinal column.

2. **Analyzing the Options**: The question provides four options regarding common characteristics of all vertebrates. We need to evaluate each option to determine which one is applicable to all vertebrates.

3. **Option 1 - Presence of Skull**: All vertebrates possess a skull that encases and protects the brain. This is a fundamental characteristic of vertebrates.

4. **Option 2 - Division of Body into Head, Neck, Trunk, and Tail**: While many vertebrates have this body division, not all do (e.g., humans do not have a tail). Therefore, this option cannot be considered a common characteristic of all vertebrates.

5. **Option 3 - Presence of Two Pairs of Functional Appendages**: This characteristic does not apply to all vertebrates, especially fish, which do not have limbs like terrestrial vertebrates. Thus, this option is also incorrect.

6. **Option 4 - Body Covered with an Exoskeleton**: Vertebrates typically have an endoskeleton (internal skeleton) rather than an exoskeleton (external skeleton). This option is incorrect as well.

7. **Conclusion**: The only characteristic that is common to all vertebrates is the presence of a skull. Therefore, the correct answer is the presence of a skull.

**Final Answer**: A common characteristic of all vertebrates is the presence of a skull.

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