In the excerpt from "The Open Window," Nuttel's observations about the room lead him to assume that Mrs. Sappleton must either be married or widowed. The mention of an "undefinable something about the room" suggesting masculine habitation indicates that he perceives the room to be reflective of the life of a woman who might have had a husband at some point, especially given the context of the tragedy mentioned by the niece. Thus, the correct response is:
He assumes Mrs. Sappleton must either be married or widowed.