**Core Concept**
Auditory fatigue refers to the temporary reduction in hearing sensitivity following exposure to loud sounds. This phenomenon is a result of the mechanical and metabolic stress experienced by the hair cells in the cochlea, leading to a reversible decrease in their sensitivity.

**Why the Correct Answer is Right**
The correct answer is related to the frequency range at which the auditory system is most susceptible to fatigue. The hair cells in the cochlea are responsible for detecting sound vibrations, and they are most sensitive to frequencies within the range of 2,000 to 5,000 Hz. Prolonged exposure to loud sounds within this frequency range can lead to auditory fatigue.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a frequency range that is commonly associated with auditory fatigue. While all frequencies can potentially cause fatigue, the range of 2,000 to 5,000 Hz is particularly susceptible.
**Option B:** This option is incorrect because it specifies a frequency that is too low to be associated with auditory fatigue. The lower frequency range (below 2,000 Hz) is less susceptible to fatigue.
**Option C:** This option is incorrect because it specifies a frequency that is too high to be associated with auditory fatigue. The higher frequency range (above 5,000 Hz) is less susceptible to fatigue.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that auditory fatigue is a reversible condition, and the hair cells in the cochlea can recover from the stress caused by loud sounds. However, repeated exposure to loud sounds can lead to permanent damage and hearing loss.

**Correct Answer:** 4000 Hz.