Answer: d. innocent
From the excerpt, it is obvious that the old man was innocent. The narrator states that the old man had never done anything wrong. He was a kind man who had never mistreated him or insulted him. The passage tells us that, in fact, the narrator has no logical reason to decide to kill the old man. It is only that his eye, which is pale blue and has a film over it (perhaps a cataract) bothers him.