Polymorphic animal is

Options

A. Physalia
B. Hydra
C. Tubipora
D. Metridium.

Answer

To determine which of the given options is a polymorphic animal, we need to understand the concept of polymorphism in animals. Polymorphism refers to the occurrence of different forms or morphs within a species.

### Step-by-Step Solution:

1. **Understand Polymorphism**:
- Polymorphism in animals means the presence of multiple distinct forms or morphs within a single species. This can include variations in structure, function, or behavior.

2. **Analyze the Options**:
- We have four options: Physalia, Hydra, Tubifora, and Metridium.

3. **Evaluate Physalia**:
- Physalia, commonly known as the Portuguese Man o' War, is a colonial organism made up of different polyps (zooids) that perform various functions such as feeding, reproduction, and defense. This indicates that Physalia exhibits polymorphism.

4. **Evaluate Hydra**:
- Hydra is a freshwater organism that is known for its regenerative abilities. However, it does not exhibit polymorphism as it generally maintains a single form throughout its life cycle.

5. **Evaluate Tubifora**:
- Tubifora refers to organisms that typically have tube-like structures, often made of calcium carbonate. These organisms do not show polymorphism as they do not have multiple forms within the species.

6. **Evaluate Metridium**:
- Metridium, also known as sea anemones, are found in marine environments. They do not exhibit polymorphism either, as they generally exist in a single form.

7. **Conclusion**:
- After evaluating all the options, the only organism that exhibits polymorphism is **Physalia**. Therefore, the correct answer is Physalia.

### Final Answer:
The polymorphic animal is **Physalia**.