The author creates suspense in this excerpt primarily through the sense of fear and dread conveyed by the narrator regarding the old man's eye. The description of the eye as having the "eye of a vulture" and "a pale blue eye, with a film over it" as well as the phrase "my blood ran cold" all contribute to creating an unsettling atmosphere.
The best answer choice that captures how suspense is built in this excerpt is:
A By identifying the source of the narrator's irrational fear.
This is because the narrator fixates on the old man's eye as the source of his fear, enhancing the sense of dread and anticipation in the narrative.