Mark the correct set showing polymorphism

Options

A. Hydra,Physalia,Obelia
B. Physalia,Porpita,Vellela
C. Physalia,Obelia,Metridium
D. Hydra,Helistema,Gorgonia

Answer

To determine the correct set showing polymorphism among the given options, we need to understand the concept of polymorphism in the context of the phylum Cnidaria, particularly within the class Hydrozoa. Here’s a step-by-step breakdown of the solution:

### Step-by-Step Solution:

1. **Understand Polymorphism**:
- Polymorphism refers to the occurrence of two or more different forms or stages in the life cycle of an organism. In Cnidarians, this is typically represented by two body forms: the polyp (sessile) and the medusa (free-swimming).

2. **Identify the Phylum and Class**:
- Polymorphism is prominently observed in the phylum Cnidaria, especially in the class Hydrozoa.

3. **Examine the Options**:
- We need to evaluate the given options to see which organisms exhibit both polyp and medusa forms.

4. **Evaluate Each Option**:
- **Option 1**: Hydra, Physalia, and Obelia.
- Hydra is a polyp only and does not have a medusa stage, so it does not show polymorphism.
- **Option 2**: Physalia, Porpita, and Velella.
- All three are part of Hydrozoa and exhibit both polyp and medusa forms, thus showing polymorphism.
- **Option 3**: Metridium.
- Metridium belongs to the class Anthozoa and does not exhibit polymorphism.
- **Option 4**: Elistema and Gorgonia.
- Both belong to Hydrozoa, but they do not exhibit both forms, hence do not show polymorphism.

5. **Conclusion**:
- The correct answer is **Option 2: Physalia, Porpita, and Velella**, as all three organisms exhibit polymorphism by having both polyp and medusa stages.

### Final Answer:
The correct set showing polymorphism is **Option 2: Physalia, Porpita, and Velella**.

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