The correct option is C vocal cords
The vocal cords produce sound when they come together and then vibrate as air passes through them during exhalation of air from the lungs. This vibration produces the sound wave for our voice.
The frequency of voice depends upon the length of the vocal cord. Shorter the vocal cord, more is the frequency and hence more shrill is the voice.
The vocal cords in men are about 20 mm long. In women these are about 5 mm shorter. Children have very short vocal cords. Due to the difference in length of vocal cords, the sounds produced by men, women and children are different.