Water vascular system is a distinctive feature of

Options

A. Echinodermata
B. Annelida
C. Chordata
D. Mollusca

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the distinctive feature of the water vascular system and which group of organisms it is associated with.

2. **Identifying the Options**: The options provided are Echinodermata, Annelida, Chordata, and Mollusca.

3. **Defining the Water Vascular System**: The water vascular system is a network of fluid-filled canals and tube feet used for various functions such as locomotion, food and waste transportation, and respiration.

4. **Associating the System with Echinodermata**: The water vascular system is specifically found in Echinoderms, which include organisms like sea stars and sea urchins.

5. **Explaining the Functionality**: In Echinoderms, the water vascular system operates by contracting muscles to force water into the tube feet, allowing them to extend and move. This is essential for their movement and interaction with the environment.

6. **Conclusion**: Based on the information, the water vascular system is a distinctive feature of Echinodermata.

### Final Answer:
The water vascular system is a distinctive feature of **Echinodermata**.

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