What is the best description of "vocal timbre"?

Vocal timbre can best be described as the quality that is unique to each individual, which is indeed determined by the characteristics of their vocal cords. This uniqueness allows listeners to differentiate between different voices, even when they are singing the same pitch. Factors such as the shape of the vocal tract, the size and structure of the vocal folds, and the way sound is articulated all contribute to a person's vocal timbre, giving each voice its distinctive sound.

While the other options reference aspects related to singing, they do not capture the essence of what timbre entails. Uniformity of sound across different voices would suggest that all voices sound the same, which contradicts the concept of timbre. The distinct musical range of a singer relates to the pitches they can comfortably sing, but this does not address the quality or color of the voice. Lastly, technique refers to the methods used for producing sound, but it does not define the inherent quality of the voice itself.