Which one of the following statements is correct about all the four of jellyfish , starfish ,platypus and pigeon ?

Options

A. Pigeon is homeothermic while the remaining three are poikilothermic
B. Starfish is a marine form while all others are freshwater forms
C. Jellyfish has cnidocytes all others lack cnidocytes
D. Starfish is radially symmetrical while all others are bilaterally symmetrical

Answer

To determine which statement is correct about jellyfish, starfish, platypus, and pigeon, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Analyze the First Statement:**
- The first statement claims that "pigeon is homeothermic while the remaining three are poikilothermic."
- Homeothermic animals maintain a constant internal body temperature (like pigeons and platypus).
- Poikilothermic animals do not have a constant body temperature (like jellyfish and starfish).
- **Conclusion:** This statement is incorrect because the platypus is also homeothermic.

2. **Analyze the Second Statement:**
- The second statement claims that "starfish is a marine form while all others are freshwater forms."
- Starfish are indeed marine animals, but jellyfish are also marine.
- Platypus and pigeon are not exclusively freshwater; they can inhabit various environments.
- **Conclusion:** This statement is incorrect because jellyfish are also marine.

3. **Analyze the Third Statement:**
- The third statement claims that "jellyfish have nidocytes and all others lack nidocytes."
- Nidocytes are specialized stinging cells found in cnidarians (which include jellyfish).
- Starfish, platypus, and pigeon do not have nidocytes.
- **Conclusion:** This statement is correct.

4. **Analyze the Fourth Statement:**
- The fourth statement claims that "starfish are radially symmetrical while all others are bilaterally symmetrical."
- Starfish exhibit radial symmetry, while the platypus and pigeon exhibit bilateral symmetry.
- Jellyfish also exhibit radial symmetry.
- **Conclusion:** This statement is incorrect because jellyfish are also radially symmetrical.

### Final Conclusion:
The correct statement about all four organisms is: **"Jellyfish have nidocytes and all others lack nidocytes."**