Reproduction takes place by only sexual means in

Options

A. Ctenophora
B. Coelenterata
C. Porifera
D. Protozoa

Answer

To solve the question "Reproduction takes place by only sexual means in," we will analyze the given options one by one to determine which organism reproduces exclusively through sexual reproduction.

### Step-by-Step Solution:

1. **Identify the Options**: The question refers to specific groups of organisms. We need to evaluate each option to see if they reproduce only through sexual means.

2. **Evaluate the First Option - Ctenophora**:
- Ctenophores (commonly known as comb jellies) primarily reproduce sexually. They have a life cycle that includes a sexual phase, and they are known for their unique method of reproduction.
- **Conclusion**: This option is correct as they reproduce only through sexual means.

3. **Evaluate the Second Option - Coelenterata**:
- Coelenterates (which include jellyfish, corals, and sea anemones) can reproduce both sexually and asexually. They often have a life cycle that includes both methods.
- **Conclusion**: This option is incorrect.

4. **Evaluate the Third Option - Porifera**:
- Poriferans (sponges) also reproduce both sexually and asexually. They can produce gametes for sexual reproduction and can also reproduce asexually through budding or fragmentation.
- **Conclusion**: This option is incorrect.

5. **Evaluate the Fourth Option - Protozoa**:
- Protozoans are a diverse group of single-celled organisms that can reproduce both sexually and asexually. Many protozoa reproduce asexually through binary fission, while some can reproduce sexually.
- **Conclusion**: This option is incorrect.

6. **Final Conclusion**:
- After evaluating all the options, we find that only Ctenophora reproduces exclusively through sexual means. Therefore, the correct answer to the question is **Ctenophora**.