The correct answer is A.
In this passage, the author creates suspense by describing a mysterious physical situation that could be a deadly trap. He is close to the edge of a large pit, so close that much of his head is hanging off the side. Poe creates suspense by the fact that the narrator close to the edge of a very deep pit.
Unpleasant details add to the sensory impact of the excerpt, but not its suspense. Furthermore, the narrator is confused in this excerpt, but not really fearful. He doesn't know enough about his current sitatuation to be afraid. Finally, the narrator becomes very quickly aware of the danger he's in -- he quickly realizes most of his head is hanging off the edge of the pit, a great danger indeed.
Therefore, Poe creates suspense by describing a mysterious physical situation that could be a deadly trap for the narrator.
