Which of the following features is unique to Mollusca ?

Options

A. Exoskeleton
B. Gill respiration
C. Unsegmented body
D. Mantle

Answer

To determine which feature is unique to Mollusca, let's analyze each option provided:

1. **Exoskeleton**:
- An exoskeleton is a hard outer structure that provides support and protection. It is commonly found in arthropods (like insects and crustaceans). Since it is not exclusive to Mollusca, this option is incorrect.

2. **Gill Respiration**:
- Gill respiration refers to the use of gills for breathing, which is a feature found in many aquatic animals, including fish. While mollusks do have gills, this characteristic is not unique to them, as it is also present in other animal groups. Therefore, this option is also incorrect.

3. **Unsegmented Body**:
- An unsegmented body means that the body is not divided into segments. This feature is found in various animal groups, including Porifera (sponges) and even in some higher organisms like humans. Thus, this option is not unique to Mollusca.

4. **Mantle**:
- The mantle is a significant feature of mollusks. It is a soft tissue layer that covers the internal organs and often secretes a shell (if present). This structure is unique to the Mollusca phylum. Therefore, this option is correct.

In conclusion, the feature that is unique to Mollusca is the **mantle**.