Comb plates occur in

Options

A. Adamsia
B. Nereis
C. Pleurobrachia
D. Aurelia

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the occurrence of "comb plates" in specific organisms. We need to identify which of the given options has comb plates.

2. **Definition of Comb Plates**: Comb plates are specialized structures that are used for locomotion. They are typically found in certain aquatic organisms and are arranged in a way that resembles cilia.

3. **Identifying the Phylum**: Comb plates are characteristic of the phylum **Ctenophora** (also known as comb jellies). This is crucial because it helps narrow down the options.

4. **Analyzing the Options**:
- **Adamsia**: This organism belongs to the phylum **Cnidaria** (jellyfish, corals, etc.), which does not have comb plates.
- **Nereus**: This organism is part of the phylum **Annelida** (segmented worms), which also does not have comb plates.
- **Plurobrachia**: This organism belongs to the phylum **Ctenophora**, which is known for having comb plates. This is a strong candidate.
- **Aurelia**: This organism is another member of the phylum **Cnidaria** and does not possess comb plates.

5. **Conclusion**: After analyzing all the options, the organism that has comb plates is **Plurobrachia**, which belongs to the phylum **Ctenophora**.

### Final Answer:
The correct answer is **Plurobrachia** (option number three).

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