question:  Which mode of exposition affects the story’s plot?
context: Her last assignment had been to interview the pilot pair riding the first American manned circum-lunar satellite—and the five alternate pairs who hadn't made the flight. Samples: "They say the Machine has been programmed to play nothing but pure Barcza System and Indian Defenses—and the Dragon Formation if anyone pushes the King Pawn." "I heard the Russians have been programmed—with hypnotic cramming and somno-briefing. Sandra's chief difficulty was that she knew absolutely nothing about the game of chess—a point that she had slid over in conferring with the powers at the Space Mirror , but that now had begun to weigh on her. It is a game for lunatics—or else it creates them. What the Machine can do is examine all the likely lines of play for about eight moves ahead—that is, four moves each for White and Black—and then decide which is the best move on the basis of capturing enemy pieces, working toward checkmate, establishing a powerful central position and so on." In crucial situations, say where there's a chance of winning at once by trapping the enemy king, he examines many more moves ahead than that—thirty or forty even. The Machine is probably programmed to recognize such situations and do something of the same sort, though we can't be sure from the information World Business Machines has released. But in most chess positions the possibilities are so very nearly unlimited that even a grandmaster can only look a very few moves ahead and must rely on his judgment and experience and artistry. The equivalent of those in the Machine is the directions fed into it before it plays a game." However, the result is that the Machine can see eight moves ahead and is capable of being programmed much more craftily." Flesh-and-blood chess masters have lost games by blunders they could have avoided by looking only one or two moves ahead. Once again, you see, you have the human factor, in this case working for the Machine."
output:  The story uses the Doc character to help paint a portrait of what Sandra cannot understand. Namely, the world of chess.
options:  The story uses the Doc character to help paint a portrait of what Sandra cannot understand. Namely, the world of chess.  The story uses the chess player characters to help paint a portrait of what Sandra cannot understand. Namely, chess.  The story uses Doc to hide the presence of Dr. Krakatower, the Frenchman responsible for defeating the WBM machines.  The story uses the machine’s astonishing capabilities to distract from the true interest of the story: the human intellect’s ability to conquer computers.