Final answer:
The mention of the Headless Horseman in The Legend of Sleepy Hollow supports the answer to part a.
Step-by-step explanation:
The detail from the story that best supports the answer to part a in The Legend of Sleepy Hollow is the mention of the Headless Horseman. Throughout the story, there are numerous references to this supernatural character, including sightings and encounters with him. This detail supports the idea that supernatural stories are prevalent in the area because of the haunted region of Sleepy Hollow.