What is the effect of the first-person narration in "there's a man in the habit of hitting me on the head with an umbrella"?

`it leads the reader to belive that the narrator is unreliable, and thus, his story cannot be believed.
`it lends a sense of believability to the absurd events, allowing the reader to suspend their disbelief.
`it gives the story a unique perspective, since the narrator is not directly involved in the events of the plot.
`it makes the story much less personal, allowing the reader to view it from an objective distance.