Read the following passage and questions, then choose the right answer from options, the answer should be one of A, B, C, D.

<passage>:
his eyebrows went up, and he made a beeline for Doc. Sandra wondered if 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. This tournament hall seemed to Sandra Circum-Terra?" "Not worth the trouble. The play was feeble. Barely Expert Rating." 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 "Okay, lead on," Sandra said. "You're the doctor." "That'd go fine." Sandra leaned back. "Confidentially, Doc, I was chess," he assured her. "It is a curse of the intellect. It is a game for lunatics—or else it creates them. But what brings a sane and beautiful young lady to this 64-square madhouse?" Sandra briefly told him her story and her predicament. By the time they were served, Doc had absorbed the one and assessed the other. "You have one great advantage," he told her. "You know nothing whatsoever of chess—so you will be able to write about it understandably for your readers." He swallowed half his demitasse and "Yes, Doc, but...." Sandra found difficulty in phrasing the question. Sandra grinned and nodded. Doc's ability to interpret her mind was as it would take them all the time there ever will be in the universe just to play through all the possible games of chess, not to mention the time needed to classify those games into branching families of wins for White, wins for Black and draws, and the additional time required to trace out chains of key-moves leading always to wins. So the Machine can't play chess like God. 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." "That sounds like the way a man would play a game," Sandra observed. "Look ahead a little way and try to make a plan. You know, like getting out trumps in bridge or setting up a finesse." genius, but who never makes a mistake. You see, you are finding human interest already, even in the Machine." Sandra nodded. "Does a human chess player—a grandmaster, I mean—ever look eight moves ahead in a game?" "Most assuredly he does! In crucial situations, say where there's a chance of winning at once by trapping the enemy king, he examines chess-playing computer. The first practical model, reported by Bernstein and Roberts of IBM in 1958 and which looked four moves ahead, was programmed so that it had a greedy worried tendency to grab only sees twice as many moves ahead?" Sandra objected. "There is a geometrical progression involved there," he told her with a smile. "Believe me, eight moves ahead is a lot of moves when you remember that the Machine is errorlessly examining every one of thousands of variations. Flesh-and-blood chess masters have lost games by blunders they could have avoided by looking only one or two moves One of the five wall chessboards was considerably larger than the other four—the one above the Machine. Sandra looked with quickening interest at the console of the Machine—a them had just laid a black cable to the nearest chess table and were attaching it to the Siamese clock. Sandra tried to think of a being who always checked everything, but playing session, Doc reordered his coffee. "One expects it of Jandorf," he explained to Sandra with a philosophic shrug when the shock-headed man was gone. "At least he didn't take your wine-and-seltzer. Or did he? One tip I have for you: don't call a chess master Mister, call him Master. They all eat it up." "Gee, Doc, I don't know how to thank you for everything. I hope I usual international rate of 15 moves an hour, and—" "Is that why they've got all those crazy clocks?" Sandra interrupted. "Oh, yes. Chess clocks measure the time each player takes in making his moves. When a player makes a move he presses a button that shuts his Doc nodded. "Not such a boy any longer, though. He's.... Well, speak of the Devil's children.... Miss Grayling, I have the honor of presenting to you the only grandmaster ever to have been ex-chess-champion of the prize will just fit the big hole in my bank account." "I know you haven't the time now, Master Angler," Sandra said rapidly, "but if after the playing session you could grant me—" charging off. Doc and Sandra looked at each other and smiled. "Chess masters aren't exactly humble people, are they?" she said. Doc's smile became tinged with sad understanding. "You must excuse them, though," he said. "They really get so little recognition or in the best temperamental-artist style. For chess players the prize money is fabulous—$35,000, with $15,000 for first place, and all expenses paid for all players. There's never been anything like it. "Yes. Now that's one with a lot of human interest. Moses Sherevsky. Been champion of the United States many times. A very strict Orthodox Jew. Can't play chess on Fridays or on Saturdays before sundown." He him . A senile has-been, it's a scandal he's been allowed to play in this tournament! He must have pulled all sorts of strings. Told them that his lifelong services to chess had won him the honor and that they very brilliant player and that the Machine is very lucky to have drawn him as its first opponent." He would not amplify his statement. Sandra studied the Scoreboard again. "By no means. That was the trouble with some of the early chess-playing machines—they were programmed by scientists. No, Simon Great is a psychologist who at one time was a leading contender for the world's chess championship. I think WBM was surprisingly shrewd to pick him for the programming job. Let me tell you—No, better yet—" Doc shot to his feet, stretched an arm on high and called out sharply, Doc spoke his piece for Sandra. games with the Machine to assure himself that it operates legitimately and has grandmaster skill." "Did the Machine beat him?" Sandra asked. famous chess-playing automaton of the 19th Century? That one too was supposed to work by machinery (cogs and gears, not electricity) but actually it had a man hidden inside it—your Edgar Poe exposed the story I think the chess robot will break down while it is being demonstrated to a millionaire purchaser and the young inventor will have to win its game for it to cover up and swing the deal. Only the millionaire's daughter, who is really a better player than either of them ... yes, yes! Your Ambrose Bierce too wrote a story about a chess-playing robot of the clickety-clank-grr kind who murdered his creator, crushing him like an iron grizzly bear imagine...." While Doc chattered happily on about chess-playing robots and chess stories, Sandra found herself thinking about him. A writer of some sort evidently and a terrific chess buff. Perhaps he was an actual medical doctor. She'd read something about two or three coming over with the this assignment completely and now she had it laid out cold. For the umpteenth time in her career Sandra shied away from the guilty thought that she wasn't a writer at all or even a reporter, she just used dime-a-dozen female attractiveness to rope a susceptible man (young,

<question>:
What role does Doc play in conjunction with Sandra?

<options>:
A He explains to Sandra that living human personality is key for beating the machine.
B He shows Sandra around the tournament.
C He explains to Sandra how the chess machine works and what the significance of each human chess player is.
D He explains the history of chess scandals to Sandra.

<answer>:

C