Why did they have to reach the summit within 18 hours?

• A. Weather forecasts demanded a quick summit.
• B. There is a limit to how long a human can stay at that altitude.
• C. Oxygen reserves are depleted after 18 hours.
• D. They planned to meet a rescue crew after 18 hours.

Answer: (B)

At very high elevations, the air is so thin that every breath carries less oxygen, and the body’s ability to function declines even with acclimatization. While climbers can adjust over days, there’s a practical time window where the risk of altitude-related illnesses—like severe headaches, nausea, or even life-threatening edema—rises with longer exposure. Reaching the summit and returning within that window minimizes the chance of those problems developing on the descent, keeping the expedition safer. The 18-hour limit isn’t about fuel or rescue plans; it reflects the physiological constraint of staying safe in extreme altitude.