A polymorphic coelenterate is

Options

A. Physalia
B. Fungia
C. Hydra
D. All the above.

Answer

To solve the question "A polymorphic coelenterate is," we need to analyze the options provided and understand the concept of polymorphism in coelenterates (Cnidarians).

### Step-by-Step Solution:

1. **Understand Polymorphism**:
- Polymorphism in coelenterates refers to the presence of more than one distinct form or life stage in the organism's life cycle. The two common forms are the polyp and the medusa.

2. **Identify the Classes of Coelenterates**:
- Coelenterates are classified into three main classes:
- **Hydrozoa**: This class exhibits both polyp and medusa forms.
- **Anthozoa**: Members of this class only have the polyp form; the medusa stage is absent or reduced.
- **Scyphozoa**: This class primarily exhibits the medusa form, with the polyp stage being either absent or very reduced.

3. **Evaluate the Options**:
- **Option 1: Physalia**: This organism is not a true coelenterate; it is a colonial organism often classified under Hydrozoa but does not fit the typical definition of polymorphism as it does not have distinct polyp and medusa forms.
- **Option 2: Fungia**: This organism belongs to the class Anthozoa, which only has the polyp form, so it cannot be considered polymorphic.
- **Option 3: Hydra**: Hydra is a member of the class Hydrozoa and exhibits both polyp and medusa forms in its life cycle, making it polymorphic.
- **Option 4: All of the above**: This option cannot be correct since not all the listed organisms exhibit polymorphism.

4. **Conclusion**:
- Based on the analysis, the only organism that qualifies as a polymorphic coelenterate is **Hydra**.

### Final Answer:
The polymorphic coelenterate is **Hydra**.