D. The poem's use of repetition — namely the tapping, the narrator's calls for Lenore, and the raven's catchphrase of "Nevermore" — contributes to the overall suspenseful, eerie mood.
This answer highlights how the various elements of repetition in the poem build a tension and reinforce the mysterious and haunting atmosphere. The continuous echoes of the tapping and the refrain "Nevermore" create a sense of inevitability and dread, enhancing the emotional weight and eerie tone of the poem.