A common characteristic of all vertebrates without exception is

Options

A. the division of body into head, neck, trunk and tial
B. their body covered with an exoskeleton
C. the possession of two pairs of functional appendages
D. the presence of well-developed skull.

Explanation

To determine a common characteristic of all vertebrates, let's analyze the options provided in the question step by step.

### Step-by-Step Solution:

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

2. **Analyzing the Options**:
- **Option A**: Division of body into head, neck, trunk, and tail.
- While many vertebrates have this division, some, like humans, do not have a tail. Therefore, this option cannot be considered a characteristic of all vertebrates.

- **Option B**: Body covered with exoskeleton.
- Exoskeletons are not present in all vertebrates. For example, mammals have an endoskeleton. Thus, this option is also not universally applicable.

- **Option C**: Possession of two pairs of functional appendages.
- While many vertebrates have limbs (like mammals), some, such as fish, do not have limbs in the same way. Hence, this option does not apply to all vertebrates.

- **Option D**: Presence of a well-developed skull.
- All vertebrates possess a skull, which protects the brain and supports the structure of the head. This is a defining characteristic of vertebrates without exception.

3. **Conclusion**:
- Based on the analysis, the common characteristic of all vertebrates without exception is the presence of a well-developed skull. Therefore, the correct answer is **Option D**.