**Core Concept**
The limit of loudness expressed as decibels that people can tolerate without substantial damage to their hearing is a critical concept in otolaryngology, specifically in the prevention of noise-induced hearing loss (NIHL). Prolonged exposure to sound levels above this threshold can cause permanent damage to the hair cells in the cochlea, leading to sensorineural hearing loss.

**Why the Correct Answer is Right**
The human ear can tolerate sound levels up to 85 decibels (dB) without significant risk of hearing damage. Sound levels above 85 dB can cause NIHL, and prolonged exposure to levels above 100 dB can lead to permanent hearing loss. The threshold of 85 dB is a crucial guideline for occupational safety and health regulations, emphasizing the importance of proper hearing protection in noisy environments. The National Institute for Occupational Safety and Health (NIOSH) recommends the use of hearing protection devices (HPDs) when working in environments where the sound level exceeds 85 dB.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a sound level that is generally accepted as the threshold for hearing damage.
**Option B:** This option is incorrect because it exceeds the recommended sound level for safe hearing exposure. Exposure to sound levels above 100 dB can lead to permanent hearing loss.
**Option C:** This option is incorrect because it is below the recommended sound level for safe hearing exposure. Sound levels below 85 dB are generally considered safe for prolonged exposure.

**Clinical Pearl / High-Yield Fact**
A common mnemonic to remember the sound level threshold for hearing damage is "85 dB: 8 hours of exposure per day, 5 days a week, with no breaks." This emphasizes the importance of regular breaks and proper hearing protection in noisy environments to prevent NIHL.

**Correct Answer: C. 85 decibels.**