Find the odd one.
(a) Sea lily
(b) Sea fan
(c) Sea cucumber
(d) Sea urchin

Options

A. Sea lily
B. Sea fan
C. Sea cucumber
D. Sea urchin

Answer

To solve the question "Find the odd one" among the given options, we will analyze each option based on their biological classification.

### Step-by-Step Solution:

1. **Identify the first option: Sea Lily (A)**
- Sea lily is also known as *Antedon*.
- It belongs to the phylum **Echinodermata**.

2. **Identify the second option: Sea Fan (B)**
- Sea fan is also known as *Gorgonia*.
- It belongs to the phylum **Cnidaria** (also known as Coelenterata).

3. **Identify the third option: Sea Cucumber (C)**
- Sea cucumber is also known as *Holothuria*.
- It belongs to the phylum **Echinodermata**.

4. **Identify the fourth option: Sea Urchin (D)**
- Sea urchin is also known as *Echinus*.
- It belongs to the phylum **Echinodermata**.

5. **Compare the classifications:**
- Sea Lily (Antedon) - Echinodermata
- Sea Fan (Gorgonia) - Cnidaria
- Sea Cucumber (Holothuria) - Echinodermata
- Sea Urchin (Echinus) - Echinodermata

6. **Determine the odd one out:**
- From the analysis, we see that Sea Lily, Sea Cucumber, and Sea Urchin all belong to the phylum Echinodermata.
- Sea Fan, on the other hand, belongs to the phylum Cnidaria.
- Therefore, the odd one out is **Sea Fan (B)**.

### Final Answer:
The odd one out is **(b) Sea Fan**.