Answer:
D). 'P' sound.
Step-by-step explanation:
Repetition is described as one of the most commonly employed literary devices that involves repetition of similar words, sentences, or phrases to emphasize a point or idea in order to make it more clear and memorable for the audience.
In the given question, Poe stresses the interruption at the door through the repetition of letter sound 'P' in 'napping, tapping, rapping, at the chamber door.' The author highlights the intervention when he says 'suddenly there came a tapping' and repeatedly uses the sound 'P' consecutively in 'rapping, rapping...door.' Therefore, option D is the correct answer.