Single protection thresholds: Extended > 84 dB for 8 hours or Peak 140 dB.

• A. Extended > 100 dB for 8 hours
• B. Extended > 84 dB for 8 hours or Peak 140 dB
• C. Peak 120 dB
• D. Extended > 70 dB for 24 hours

Answer: (B)

The question centers on how single-protection exposure thresholds are defined for hearing safety: one limit for long, continuous noise and a separate limit for brief, impulsive peaks. The standard limits state that safe exposure is an extended threshold of 84 dB over 8 hours, or a peak threshold of 140 dB. The correct option matches both parts, reflecting the two ways to protect hearing: keep sustained noise below 84 dB for an 8-hour period, and ensure peak impulses do not exceed 140 dB.

Why this is best: it directly aligns with the established protection rules that govern both continuous exposure and instantaneous peaks. The other choices don’t fit because they either misstate the extended limit (for example, 100 dB over 8 hours is not the recognized threshold) or misstate the peak limit (120 dB is below the 140 dB cap, and the statement would be incomplete without the extended limit), or combine an incorrect duration with an inappropriate threshold (such as 70 dB for 24 hours).