Read the excerpt from Poe’s "The Fall of the House of Usher." No sooner had these syllable passed my lips, than -- as if a shield of brass had indeed, at the moment, fallen heavily upon a floor of silver -- I became aware of a distinct, hollow, metallic, and clangorous, yet apparently muffled reverberation. Completely unnerved, I leaped to my feet; but the measured rocking movement of Usher was undisturbed.

Which word from this excerpt could be used to argue that the narrator is unreliable?
A. “Passed” suggests the narrator’s lack of control.
B. “Aware” suggests the narrator’s struggle to observe.
C. “Unnerved” suggests the narrator’s nervousness.
D. “Undisturbed” suggests the narrator’s lack of reaction.