Final answer:
Krakauer faced a bottleneck of climbers at the Hillary Step on Mount Everest, causing dangerous delays during descent.The correct option is c.
Step-by-step explanation:
Jon Krakauer, author of 'Into Thin Air,' encountered a bottleneck of climbers at the Hillary Step after descending from the summit of Mount Everest. This congestion is caused by the narrow pathway of the Hillary Step that climbers must pass through, which can become a choke point, especially when large numbers of climbers are attempting to summit on the same day. The overcrowding can lead to significant delays and can be quite dangerous due to the exposure and fatigue that climbers experience at such high altitudes.