Final answer:
Jon Krakauer was alone at the summit of Mount Everest initially. Neither Doug Hansen nor Rob Hall was with him at the top as they were still ascending. The provided options do not accurately reflect the true events as per Krakauer's account.
Step-by-step explanation:
The question pertains to Jon Krakauer's account of his experience climbing Mount Everest, which he wrote about in his non-fiction book 'Into Thin Air'. When Krakauer reached the summit, he was alone because his initial climbing partner, Andy Harris, had turned back earlier. Later on the descent, Krakauer passed other climbers including Doug Hansen and Rob Hall.
According to Krakauer's account, none of the options provided accurately describe who was with him at the top of the mountain. However, if we must choose the closest scenario from the options given, it would be b) Rob Hall arrived first, and Doug Hansen arrived after Krakauer, although it is not accurate to the events as described. Krakauer had reached the summit ahead of Hall and Hansen.