**Core Concept**
Auditory fatigue is a condition characterized by a decrease in the sensitivity of the auditory system due to prolonged exposure to sound. It is an important consideration in the field of audiology and hearing conservation, particularly in individuals who work in noisy environments.

**Why the Correct Answer is Right**
The correct answer is based on the concept of the auditory threshold, which is the minimum intensity of sound that can be perceived by a person. Auditory fatigue occurs when the auditory threshold is elevated due to prolonged exposure to sound, particularly at frequencies above 2000 Hz. This is because the hair cells in the cochlea are more sensitive to high-frequency sounds and are more susceptible to damage from prolonged exposure. The specific frequency at which auditory fatigue occurs is related to the concept of the "noise notched audiogram," which shows a significant loss in hearing sensitivity at the frequency of the noise exposure.

**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect because auditory fatigue typically occurs at frequencies above 2000 Hz, not below.
**Option B:** This is incorrect because auditory fatigue is not typically associated with frequencies below 200 Hz, which is more commonly associated with low-frequency hearing loss.
**Option C:** This is incorrect because auditory fatigue is not typically associated with frequencies above 8000 Hz, which is more commonly associated with high-frequency hearing loss.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that auditory fatigue is a reversible condition, meaning that hearing sensitivity can return to normal once the individual is removed from the noisy environment.

**Correct Answer: C. 4000 Hz**