Select the correct statement

Options

A. All arthropods have at least one pair of antennae
B. All molluscs have an external or internal shell
C. All annelids have setae
D. All echinoderms have water vascular system.

Answer

To solve the question of selecting the correct statement regarding various animal phyla, we can follow these steps:

### Step-by-Step Solution:

1. **Analyze the First Statement**:
- The statement claims that "all arthropods have at least one pair of antennae."
- **Evaluation**: This is incorrect because members of the class Arachnida (e.g., spiders and scorpions) do not have antennae.

2. **Analyze the Second Statement**:
- The statement claims that "all mollusks have an external or internal shell."
- **Evaluation**: This is also incorrect. For example, octopuses and squids are mollusks that do not possess any type of shell.

3. **Analyze the Third Statement**:
- The statement claims that "all annelids have setae."
- **Evaluation**: This statement is incorrect as well. Certain annelids, such as dinophilus, do not have setae.

4. **Analyze the Fourth Statement**:
- The statement claims that "all echinoderms have a water vascular system."
- **Evaluation**: This statement is correct. The water vascular system is indeed a defining characteristic of echinoderms, which includes starfish and sea urchins.

5. **Conclusion**:
- After evaluating all the statements, the only correct statement is that "all echinoderms have a water vascular system."

### Final Answer:
The correct statement is: **All echinoderms have a water vascular system.**

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