The correct answer is B. After hiking for hours, the hikers saw the rest area appear in the near distance.
Step-by-step explanation:
The original sentence or "After hiking for hours the rest area appeared in the near distance" aims at explaining some hikers had been hiking for hours and then they could see the rest area in the near distance; however, this meaning is not completely clear because in the original sentence it is not explicitly stated who was the person or entity that hiked for hours and then saw the rest area instead it is stated the rest area appeared which creates a confusing sentence.
Considering this, the best revision for this sentence would be to state it the entity or agent of the action and change the word "appear", therefore, the best revision is "After hiking for hours, the hikers saw the rest area appear in the near distance" as this explicitly states the "hikers" were the ones that hiked for hours and then they saw the rest are, which corrects the mistakes of the original sentence.