Which of the followins is vestigial in humans

Options

A. Mammaary glands in males
B. Knee bones
C. Nictitating membrane
D. Ear pinna

Answer

**Step-by-Step Solution:**

1. **Understanding Vestigial Organs**: Begin by defining what vestigial organs are. Vestigial organs are those that have lost most or all of their original function through the course of evolution.

2. **Identifying Options**: The options provided in the question are:
- Mammary gland in males
- Knee bones
- Nictitating membrane
- Ear fin

3. **Analyzing Each Option**:
- **Mammary gland in males**: While it does not serve the same function as in females, it is not entirely vestigial as it can still produce milk under certain conditions.
- **Knee bones**: These are fully functional and play a critical role in movement and support.
- **Nictitating membrane**: This is a small fold of tissue in the corner of the eye that is considered vestigial in humans as it no longer serves its original purpose of protecting and moistening the eye.
- **Ear fin**: This term is not commonly used in human anatomy; it may refer to structures related to ear muscles, which are also vestigial but not as widely recognized as the nictitating membrane.

4. **Conclusion**: Among the options given, the nictitating membrane is recognized as a vestigial structure in humans, as it has lost its original function in protecting the eye.

5. **Final Answer**: The correct answer is the **Nictitating membrane**.

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