Bioluminescence is well marked in

Options

A. protozoa
B. ctenophores
C. cnidarians
D. sponges

Answer

**Step-by-Step Solution:**

1. **Understanding Bioluminescence**: Bioluminescence is the ability of living organisms to produce and emit light. This phenomenon is observed in various organisms across different taxa.

2. **Identifying the Options**: The question provides four options:
- A. Protozoa
- B. Cnidarians
- C. Tenophores
- D. Sponges

3. **Analyzing Each Option**:
- **Protozoa**: Some protozoans exhibit bioluminescence, but it is not a well-marked characteristic across the group.
- **Cnidarians**: While some cnidarians (like certain jellyfish) can exhibit bioluminescence, it is not as prominent as in other groups.
- **Tenophores**: This group, also known as comb jellies, is well-known for its bioluminescent properties. They are marine organisms that exhibit this trait prominently.
- **Sponges**: Sponges do not exhibit bioluminescence.

4. **Conclusion**: Based on the analysis, the group where bioluminescence is well marked is the Tenophores.

5. **Final Answer**: The correct answer is C. Tenophores.

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