Read the excerpt from "The Tell-Tale Heart.”

TRUE!—nervous—very, very dreadfully nervous I had been and am; but why will you say that I am mad? The disease had sharpened my senses—not destroyed—not dulled them. Above all was the sense of hearing acute. I heard all things in the heaven and in the earth. I heard many things in hell. How, then, am I mad? Hearken! and observe how healthily—how calmly I can tell you the whole story.

Which statement best explains how the reader can determine that the narrator of this passage is unreliable?

The narrator is very calm as he begins to relate all of the events of the story.
The narrator worries that his dreadful nervousness has caused him to go mad.
The narrator says he is not mad, but he claims he can hear all the sounds on heaven and earth.
The narrator has sharpened senses that allow him to hear sounds that others cannot.