What is the minimum concentration of H2S that will cause death with short-term exposure?

Correct Answer: Option D — 700 ppm

H2S is a highly toxic, colorless gas. At 700 ppm, the concentration is sufficient to cause rapid respiratory failure and death upon short-term exposure. This level is considered immediately dangerous to life and health (IDLH), requiring immediate evacuation and the use of self-contained breathing apparatus (SCBA) for any entry.