Which of the following is true of adaptation, one of the basic elements of the techniques of good talking?

A) It refers to the pitch and resonance of the sounds a speaker makes and the sounds an audience hears.
B) It refers to a set of voice behaviors that gives each person a unique voice.
C) It varies in messages delivered in different cultures as well as different social situations, work situations, and classrooms.
D) It is difficult for a speaker to adapt himself or herself to the audience if he or she has a large vocabulary.
E) It is independent of the speaker's style and voice.

Adaptation refers to the ability to adjust one's communication style, tone, and message to fit the audience and the situation. This includes understanding how culture and context influence communication. Therefore, option C is the most accurate description of adaptation among the given options. Option A refers to vocal variety, which is a related but distinct concept. Option B refers to individual vocal characteristics, which are not necessarily adaptable. Option D is incorrect because having a large vocabulary does not hinder a speaker's ability to adapt to the audience. Finally, adaptation is dependent on the speaker's style and voice, as it involves modifying one's communication style to better suit the audience.