From "the tell tale heart" by edgar allen poe
now this is the point. you fancy me mad. madmen know nothing. but you should have seen me. you should have seen how wisely i proceeded --with what caution --with what foresight --with what dissimulation i went to work! i was never kinder to the old man than during the whole week before i killed him. and every night, about midnight, i turned the latch of his door and opened it --oh so gently! and then, when i had made an opening sufficient for my head, i put in a dark lantern, all closed, closed, that no light shone out, and then i thrust in my head. oh, you would have laughed to see how cunningly i thrust it in! i moved it slowly --very, very slowly, so that i might not disturb the old man's sleep. it took me an hour to place my whole head within the opening so far that i could see him as he lay upon his bed. ha! would a madman have been so wise as this, and then, when my head was well in the room, i undid the lantern cautiously-oh, so cautiously --cautiously (for the hinges creaked) --i undid it just so much that a single thin ray fell upon the vulture eye. and this i did for seven long nights --every night just at midnight --but i found the eye always closed; and so it was impossible to do the work; for it was not the old man who vexed me, but his evil eye. and every morning, when the day broke, i went boldly into the chamber, and spoke courageously to him, calling him by name in a hearty tone, and inquiring how he has passed the night. so you see he would have been a very profound old man, indeed, to suspect that every night, just at twelve, i looked in upon him while he slept.
what does the narrator mention to prove his sanity in this paragraph?
a) he mentions how only crazy people declare themselves not to be crazy.
b) he draws the reader's attention to how in reality the old man was quite evil, though he seemed harmless.
c) he admits that he is slightly out of his mind, but declares that anyone would be, under these circumstances.
d) he draws the reader's attention to how carefully and methodically he approaches the commission of his murder.