Bioluminescence is well marked in

Options

A. Fasciola
B. Pleurobranchia
C. Adamsia
D. Ascaris

Answer

To solve the question "Bioluminescence is well marked in," we will analyze the given options step by step.

### Step 1: Understand Bioluminescence
Bioluminescence is the ability of certain organisms to produce and emit light. This phenomenon is primarily found in some marine organisms, particularly those belonging to specific phyla.

### Step 2: Analyze the Options
The options provided are:
- A. Fasciola
- B. Pleurobranchia
- C. Adamasia
- D. Ascaris

### Step 3: Identify the Phyla
1. **Fasciola**: This is a genus of flatworms (trematodes), specifically liver flukes. They do not exhibit bioluminescence.
2. **Pleurobranchia**: This organism belongs to the phylum Ctenophora (comb jellies), which are known for their bioluminescent properties.
3. **Adamasia**: This is a genus of marine gastropods, which do not exhibit bioluminescence.
4. **Ascaris**: This is a genus of parasitic roundworms (nematodes) and does not exhibit bioluminescence.

### Step 4: Conclusion
Among the given options, **Pleurobranchia** is the only organism that is well-known for its bioluminescent properties. Therefore, the correct answer is:

**Answer: B. Pleurobranchia**

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