Presence of nitrogen in high concentration in contaminated air reduces partial pressure of oxygen in lungs, thereby causing asphyxia (suffocation) leading to death from oxygen deficiency. Concentration of N₂ in contaminated air at which it acts as a natural asphyxant is ≥ __________ percent.

• A. 80
• B. 84
• C. 88
• D. 92

Answer: (B)