**Length of vocal cords in men**

The correct answer is option 'D', which states that the length of vocal cords in a man is about 20mm.

**Explanation**

Vocal cords are an essential part of the human voice production system. They are located in the larynx, also known as the voice box, which is situated in the neck. When we speak or produce sound, the air from our lungs passes through the vocal cords, causing them to vibrate and produce sound waves.

The length of vocal cords can vary between individuals based on several factors, including age, sex, and physical characteristics. In general, the vocal cords of adult males tend to be longer and thicker than those of adult females. This difference in length and thickness results in a deeper pitch of voice in males compared to females.

**Average length of vocal cords in men**

The average length of vocal cords in adult males is around 20mm. However, it is important to note that this measurement may vary slightly between individuals. Some men may have slightly longer or shorter vocal cords based on their unique physiology.

**Importance of vocal cord length**

The length of vocal cords directly affects the pitch of an individual's voice. Longer vocal cords vibrate at a slower rate, producing a lower pitch, whereas shorter vocal cords vibrate at a faster rate, resulting in a higher pitch.

In men, the longer vocal cords contribute to the deeper pitch of their voices compared to women. This is because the vibrations produced by longer vocal cords create lower frequency sound waves.

**Conclusion**

In conclusion, the length of vocal cords in adult men is approximately 20mm. This length contributes to the deeper pitch of their voices compared to women. However, it is important to remember that individual variations may exist, and the precise length of vocal cords can vary slightly between individuals.