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

<passage>:
The garden stretched off in unthinkable immensity to the cluster of plants could live out there as they did within the world, then so could people. Rikud and his people should . This was why the world had moved across the darkness and the stars for all Rikud's lifetime and more. Galaxy Science Fiction September 1951. Extensive research did not uncover any evidence that they were so alien, so unnatural. But ever since the engines somewhere in the rear of the world had changed their tone, realized this odd difference in himself, he kept it locked up inside him. Today, space looked somehow different. The stars—it was a meaningless concept to Rikud, but that was what everyone called the bright If he had understood the term, Rikud would have told himself this was odd. His head ached with the half-born thought. It was—it was—what was it? children. And all you can do in the meantime is gaze out at the stars." could live and that was why the world had moved through the blackness, He stared out into the garden, and off into the distance, where the blue-white globe which might have been a star stood just above the row of mounds. embroiled him in a hopeless, infinite confusion that left him with a the floor, and sometimes he looked at the blue-white globe on the Rikud muttered to himself and undressed. The world had begun to annoy That is, if those creatures coming from the ship are people." "They're women," said Crifer. They were strangely shaped in some ways, and yet in others completely It was much better than the small world of machinery, buzzer, there should have been authority. A long time ago the reading machine in the library had told him of the elders—a meaningless term—who had governed the world. They told you to do something and you did it, but that was silly, because now no one told you to do anything. You only that could have no reality outside of the reading machine—and the had decided that they did not know where they were going, or why, and before Rikud's time, had negated the necessity for a knowledge of meant that, in the two unoccupied hours before sleep, he went to the library and listened to the reading machine. Everyone else simply sat about and talked. That was the custom. Everyone did it. people ever talked about was what they had done during the day, and it was always the same. "Yes," said Crifer. "I found a book about the stars. They're also called astronomy, I think." This was a new thought to Rikud, and he propped his head up on one elbow. "What did you find out?" "That's about all. They're just called astronomy, I think." "Well, where's the book?" Rikud would read it tomorrow. "I left it in the library. You can find several of them under 'astronomy,' with a cross-reference under 'stars.' They're synonymous terms." "You know," Rikud said, sitting up now, "the stars in the viewport are changing." "Changing?" Crifer questioned the fuzzy concept as much as he questioned what it might mean in this particular case. "Yes, there are less of them, and one is bigger and brighter than the others." "Astronomy says some stars are variable," Crifer offered, but Rikud knew his lame-footed companion understood the word no better than he did. them, "is a contradictory term. Nothing is variable. It can't be." "I'm only saying what I read in the book," Crifer protested mildly. "Well, it's wrong. Variability and change are two words without meaning." "People grow old," Rikud suggested. concepts, yet it was so clear. Or was it? He had had it a moment ago, but now it faded, and change and old were just two words. world, however, he paused. He wanted to open that door and see a woman. globe—if, indeed, that was the star Rikud had seen earlier? There was that word change again. Didn't it have something to do with age? Rikud couldn't remember, and he suddenly wished he could read Crifer's book on astronomy, which meant the same as stars. Except that it was variable, which was like change, being tied up somehow with age. that it spread out over almost the entire surface. Something big and round, all grays and greens and browns, and something for which Rikud had no name. nothing but an obscuring cloud of white vapor, murky, swirling, more vapor. "What do you see?" vaster than the gardens, although all of it existed in the viewport which was no wider than the length of his body. The gardens, moreover, The world had come to rest on the garden of the viewport. it as fact. There—through the viewport and in it—was a garden. A garden larger than the entire world, a garden of plants which Rikud had world's garden and he had come to know every plant well. Nevertheless, it was a garden. viewport could mean only one thing. The world had been walking—the it were running. The world had been walking somewhere. That somewhere was the garden and the world had arrived. "It is an old picture of the garden," Chuls suggested, "and the plants are different." Where are they, Chuls, if it did not change?" shine during the day when the world wants them to shine only at night?" "Naturally," said Crifer, becoming interested. "They are variable." Rikud regretted that he never had had the chance to read that book on astronomy. He hadn't been reading too much lately. The voice of the reading machine had begun to bore him. He said, "Well, variable or not, our whole perspective has changed." obvious. If he, Rikud, walked from one part of the world to another, it was with a purpose—to eat, or to sleep, or perhaps to bathe in the health-rays. Now if the world had walked from—somewhere, through the vast star-speckled darkness and to the great garden outside, this also was purposeful. The world had arrived at the garden for a reason. But if everyone lived as if the world still stood in blackness, how could they find the nature of that purpose? machine and book on astronomy or stars in his lap, Rikud approached the door. "What's in here?" he demanded. "It's a door, I think," said Crifer. "I know, but what's beyond it?" "Beyond it? Oh, you mean through it. It's only a door." There's nothing. It just isn't. It's only a door, Rikud." is a perfect, self-sustaining world. It is more than that: it is words. What in the world was an unauthorized person? More interesting gears and wheels and nameless things all strange and beautiful because they shone with a luster unfamiliar to him. "Odd," Rikud said aloud. Then he thought, "Now there's a good word, but no one quite seems to know its meaning." viewport stood on the other end of the world. It did seem smaller, and, book on astronomy. Chuls did not believe Rikud at all. "There are not that many doors in the world," he said. "The library has a door and there is a door to the women's quarters in five years, the Calculator will send you through that. But there are no others." the world, there are two other doors!" "Doing what?" has been imagining things, why should I?" though. Maybe then he could take them outside with him to the big machinery. For a long time he watched the wheels and cogs and gears was a shambles of twisted, broken metal. He laughed, softly at first, clearly. All else was bathed in a shadow of unreality. eat or drink. Rikud himself had fumbled through the blackness and the "What won't?" "It was not bad. The world has moved through the blackness and the eat. I hate Rikud, I think." There was a lot of noise in the darkness, and someone else said, "I hate Rikud." Then everyone was saying it.

<question>:
What do the characters refer to as "the world?"

<options>:
A Their ship, which is all they have ever known.
B The men's quarters, which is all they have ever known.
C The planet they are preparing to plummet onto.
D They use it as a general term for the "universe."

<answer>:

A