Which of the following molluses have asymmetry due to torsion ?

Options

A. Pila
B. Teredo
C. Dentalium
D. Octopus

Answer

To determine which mollusks exhibit asymmetry due to torsion, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Torsion**: Torsion is a developmental process in certain mollusks where the body twists 180 degrees, leading to asymmetry. This is a key characteristic of some molluscan classes.

2. **Identify Classes of Mollusks**: The phylum Mollusca is divided into several classes. The main classes include:
- Aplacophora
- Monoplacophora
- Polyplacophora
- Gastropoda
- Bivalvia
- Cephalopoda
- Scaphopoda (also known as tusk shells)

3. **Focus on Gastropoda**: Among these classes, the class that is known for exhibiting torsion is Gastropoda. This class includes snails and slugs, which are characterized by their twisted body structure.

4. **Analyze the Options**: The options given are:
- A) Pila
- B) Pterido
- C) Dentalium
- D) Octopus

5. **Identify the Snails**:
- **Pila**: Commonly known as the apple snail, which belongs to the Gastropoda class and exhibits torsion.
- **Pterido**: Not a snail, does not exhibit torsion.
- **Dentalium**: Known as tusk shells, does not exhibit torsion.
- **Octopus**: A cephalopod, does not exhibit torsion.

6. **Conclusion**: Since Pila is the only option that represents a snail and belongs to the class Gastropoda, which is known for torsion, the correct answer is option A) Pila.

### Final Answer:
The mollusk that exhibits asymmetry due to torsion is **A) Pila**.

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