Which of the following best shows that annelids and arthropods are closely related ? Both :

Options

A. have a complete digestive tract
B. have a ventral solid nerve cord
C. are segmented
D. have a tube-within-a-tube body plan

Explanation

To determine which characteristic best shows that annelids and arthropods are closely related, we can analyze the given options step by step.

### Step 1: Understand the Characteristics
We have the following options to consider:
1. They have a complete digestive tract.
2. They have a ventral solid nerve cord.
3. They are segmented.
4. They have a tube within tube body plan.

### Step 2: Analyze Each Option
- **Complete Digestive Tract**: While both annelids and arthropods have a complete digestive tract, this feature is also found in many other animal groups, making it less indicative of a close relationship.

- **Ventral Solid Nerve Cord**: This is another common feature found in many invertebrates, not just annelids and arthropods. Therefore, it does not strongly indicate a close relationship.

- **Segmented**: Both annelids (like earthworms) and arthropods (like insects and crustaceans) exhibit segmentation in their body structure. This is a significant feature that suggests a closer evolutionary relationship.

- **Tube Within Tube Body Plan**: This is a general characteristic of many animals, including those outside of annelids and arthropods, so it does not specifically indicate a close relationship between the two groups.

### Step 3: Conclusion
The best option that shows that annelids and arthropods are closely related is:
**C. They are segmented.**

### Final Answer
The correct option is **C. They are segmented.**

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