The eye lids of frog that protect them while in water is 

Options

A. upper eye lid
B. lower eye lid
C. 1 & 2
D. Nictitating membrane

Answer

To answer the question about which eyelid of the frog protects them while in water, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Options**: The options given are:
- Upper eyelid
- Lower eyelid
- Both upper and lower eyelids
- Nictitating membrane

2. **Analyzing the Upper Eyelid**:
- The upper eyelid of a frog is thick and primarily functions to keep the eye moist and clean.
- It does not provide protection while the frog is in water.

3. **Analyzing the Lower Eyelid**:
- The lower eyelid also does not serve the purpose of protecting the eye while submerged in water.
- Therefore, this option is also incorrect.

4. **Analyzing the Nictitating Membrane**:
- The nictitating membrane, often referred to as the "third eyelid," is a semi-transparent membrane that can cover the eye.
- This membrane allows frogs to see underwater while also providing protection from predators and debris.

5. **Conclusion**:
- Since the nictitating membrane serves the purpose of protecting the eye and aiding visibility in water, it is the correct answer to the question.

### Final Answer:
The eyelids of the frog that protect them while in water is the **nictitating membrane**.

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