The correct answer is the following: option d. By referring to the lightning-rod man as Mr. Jupiter Tonans, a pagan god, the narrator is calling the salesman a pagan as well.
"The Lightning-Rod Man" is a short story written by American author Herman Miller and first published on "The Piazza Tales" in 1856. It tells the story of a door-to-door salesman of lightning rods while he attempts to sell his product to a sales resistant narrator while a terrific thunder storm is occurring.
When the narrator calls the sales man by the name of Jupiter Tonans which is the name of a pagan god, he is making an allusion that the salesman is pagan as well. That is why the sales man responds by saying "call me not by that pagan name" as he understood the meaning behind the name that the narrator just called him.
