Reproduction takes place by only sexual means in

Options

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

Answer

To determine which group of organisms reproduces only by sexual means, we need to analyze each of the given options: Tenophora, Cnidaria, Porifera, and Protozoa.

### Step-by-Step Solution:

1. **Understanding the Options**:
- **Tenophora**: This phylum includes organisms known as comb jellies. They are known for their unique method of locomotion using cilia and have a complex reproductive system.
- **Cnidaria**: This phylum includes jellyfish, corals, and sea anemones. They can reproduce both sexually and asexually.
- **Porifera**: This phylum includes sponges. They primarily reproduce asexually through processes like fragmentation.
- **Protozoa**: These are single-celled organisms that can reproduce both sexually and asexually, often through binary fission.

2. **Analyzing Reproductive Methods**:
- **Tenophora**: Reproduction occurs only through sexual means. They have both male and female reproductive organs, but they are not separate sexes.
- **Cnidaria**: They can reproduce asexually (e.g., budding) and sexually (e.g., through gametes).
- **Porifera**: They primarily reproduce asexually through fragmentation, although some can reproduce sexually.
- **Protozoa**: Most protozoa reproduce asexually (e.g., binary fission), but some can reproduce sexually.

3. **Conclusion**:
- Based on the analysis, the only group that reproduces exclusively through sexual means is **Tenophora**.

### Final Answer:
Reproduction takes place by only sexual means in **Tenophora**.

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