Find out the odd one
(a) Adamsia
(b) Astraea
(c) Physalia
(d) Pleurobrachia

Options

A. Adamsia
B. Astraea
C. Physalia
D. Pleurobrachia.

Answer

To find the odd one out among the given options, we need to analyze each organism based on their classification and characteristics.

### Step-by-Step Solution:

1. **Identify the Organisms:**
- (a) Adamsia
- (b) Astraea
- (c) Physalia
- (d) Pleurobrachia

2. **Classify Each Organism:**
- **Adamsia:** This organism is a type of sea anemone and belongs to the phylum **Cnidaria** (or Coelenterata).
- **Astraea:** This is a genus of sea stars, which also belongs to the phylum **Cnidaria**.
- **Physalia:** Commonly known as the Portuguese man o' war, this organism is also classified under the phylum **Cnidaria**.
- **Pleurobrachia:** Known as sea gooseberry, this organism belongs to the phylum **Ctenophora** (or Acnidaria).

3. **Determine the Odd One Out:**
- The first three organisms (Adamsia, Astraea, and Physalia) all belong to the phylum **Cnidaria**.
- The last organism, **Pleurobrachia**, belongs to a different phylum, **Ctenophora**.

4. **Conclusion:**
- Since Pleurobrachia is the only organism that does not belong to the phylum Cnidaria, it is the odd one out.

### Final Answer:
The odd one out is **(d) Pleurobrachia**.

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