"and have i not told you that what you mistake for madness is but overacuteness of the senses?--now, i say, there came to my ears a low, dull, quick sound, such as a watch makes when enveloped in cotton. i knew that sound well, too. it was the beating of the old man's heart in the passage provided and in several other places in the story "the tell-tale heart", the narrator tries to convince the reader that he is not mad. which effect does his insistent repetition have on the reader?

A. the narrator implies to the reader that the story is just a dream.
B. the narrator convinces the reader that the reader is mad.
C. the narrator proves to the reader that he is mad.
D. the narrator shows the reader that he is not mad.