The correct answer is D. The narrator in "Exhalation" most crearly changes from the beginning to the end of the story in the sense that at the story's beginning, he is a methodical thinker, but by the end, he becomes more introspective.
The narrator begins the story scientifically analizing why a number of clocks appear to be running fast simultaneously but not malfunctioning per se. He decides to dissect their own brain and studies it methodically. By the end of the story, however, he is pondering the possible existence of other universes and marvelling at the importance of equilibrium, which is less methodical and scientific and more philosophical and abstract, hence, introspective.
