I don’t understand what this means

Final test. which theme is conveyed in this excerpt from "the tell-tale heart" by edgar allan poe? 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. it is impossible to say how first the idea entered my brain; but once conceived, it haunted me day and night. object there was none. passion there was none. i loved the old man. he had never wronged me. he had never given me insult. for his gold i had no desire. i think it was his eye! yes, it was this! he had the eye of a vulture—a pale blue eye, with a film over it. whenever it fell upon me, my blood ran cold; and so by degrees—very gradually—i made up my mind to take the life of the old man, and thus rid myself of the eye forever. a. the insane have no sense of time. b. the insane are obsessed with mortality. c. the insane are incapable of using deception. d. the insane lack imagination. e. the insane live in a reality of their own.