Nictitating membrane is useful to frog in

Options

A. far sight
B. short sight
C. covering and protecting eye ball from mud and water
D. covering and protecting eye lids from mud and other particles.

Answer

### Step-by-Step Solution:

1. **Understanding the Nictitating Membrane**: The nictitating membrane is a thin, transparent membrane that is found in the eyes of certain animals, including frogs. It serves as an additional eyelid.

2. **Function of the Nictitating Membrane**: The primary function of the nictitating membrane is to protect the eye. It can cover the eyeball while still allowing for some vision. This is particularly important for amphibians like frogs, which live both in water and on land.

3. **Protection from Environmental Factors**: Frogs often encounter environments that can be harsh on their eyes, such as muddy waters or debris. The nictitating membrane helps shield the eyeball from mud, water, and other particles that could impair vision or cause injury.

4. **Evaluating the Options**:
- Option 1 (farsight) and Option 2 (short sight) are incorrect as the nictitating membrane does not specifically aid in vision correction.
- Option 3 states that it covers and protects the eyeball from mud and water, which aligns with the function of the nictitating membrane.
- Option 4 mentions covering and protecting eyelids from mud and other particles, which is not accurate since the nictitating membrane protects the eyeball directly, not the eyelids.

5. **Conclusion**: Based on the analysis, the correct answer is Option 3: "covering and protecting eyeball from mud and water."