Which of the following is not a vestigial organ?

Options

A. Scalp hair
B. Epiglottis
C. Vermiform appendix and nictitating membrane of the eye
D. Wisdom tooth

Answer

To determine which of the following is not a vestigial organ, we need to first understand what vestigial organs are. Vestigial organs are those that have lost their original function through the course of evolution and are often smaller or simpler than their counterparts in related species.

### Step-by-Step Solution:

1. **Understand the Definition of Vestigial Organs**:
- Vestigial organs are remnants of structures that had a function in ancestral species but are no longer functional or have reduced functionality in the current species.

2. **Identify Common Examples of Vestigial Organs**:
- Some well-known examples of vestigial organs include:
- The human tailbone (coccyx)
- The vermiform appendix
- Wisdom teeth
- Plica semilunaris (the small fold of tissue in the inner corner of the eye)

3. **Analyze the Given Options**:
- Look at the options provided in the question. For each option, determine whether it is a vestigial organ or not.
- For example:
- **Scalp hair**: This is not a vestigial organ; it serves a purpose (protection, insulation).
- **Vermiform Appendix**: This is a vestigial organ.
- **Wisdom Tooth**: This is also a vestigial organ.
- **Epiglottis**: This is not a vestigial organ; it plays an important role in preventing food from entering the windpipe.

4. **Determine the Correct Answer**:
- From the analysis, the epiglottis is the only option that is not a vestigial organ. It performs a critical function in the body.

### Conclusion:
The correct answer to the question "Which of the following is not a vestigial organ?" is **Epiglottis**.