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

<passage>:
city of metal that glittered malignantly before the cautious advance of three awed space-scouters. edge of the city. Behind them the black pile rose, the dome of force shimmering, almost invisible, about it. usually exercises in a situation where the totally unexpected has occurred, and he and his two companions sat and stared in awed silence at the city a quarter-mile away. He saw the dull, black walls of buildings shouldering grimly into the twilight sky, saw the sheared edge where the metal city ended and the barren earth began ... and he remembered observing, even before they landed, the too-strict geometry imposed on the entire construction. He frowned. The first impression was ... malignant. a graceful movement of hand and arm he indicated the waiting city. Martin led Wass, and the gangling, scarecrow-like Rodney, through the sky, and harsh and black against it, the convoluted earth. And the city. Malignant. He wondered, again, what beings would choose to build a city—even a city like this one—in such surroundings. The men from the ship knew only the surface facts about this waiting in their ships, had not spotted the city. But the eleventh expedition city on the planet—the planet without any life at all, save tiny mosses, for a million years or more. And no matter which direction from the city a man moved, he would always be going north. After a time, Wass said, "Here, too. How far do you think it goes?" Martin shrugged. "Clear around the city? I'd like to know what it is—was—for." "Defense," Rodney, several yards behind, suggested. The three crossed the metal band and walked abreast down a street, their broad soft soled boots making no sound on the dull metal. They passed doors and arches and windows and separate buildings. They moved cautiously across five intersections. And they stood in a square surrounded by the tallest buildings in the city. Rodney broke the silence, hesitantly. "Not—not very big. Is it?" Wass looked at him shrewdly. "Neither were the—well, shall we call them, people? Have you noticed how low everything is?" "If we don't hurry up and get through this place and back to the ship, looked back along the straight, metal street they'd walked on, and past that out over the bleak, furrowed slopes where the ship's lifeboat lay ... and he thought everything outside the city seemed, somehow, from here, a little dim, a little hazy. He straightened his shoulders. The city was alien, of course, and that explained most of it ... most of it. But he felt the black city was something familiar, yet twisted and distorted. "Well," Wass said, his nose wrinkling a bit, "now that we're here...." There was a pause. Then Wass, defensively—"It's almost as if the city didn't want to be photographed." Parallel evolution on two inner planets of the same system? Somewhere, sometime, a common ancestor? Martin noted the shoulder-high doors, the heavier gravity, remembered the inhabitants of the city vanished before and glittering, as far as I can see. I can't get across it it's like a "No go," Martin said to Wass. He bit at his lower lip. "I think it must be all around us." He was silent for a time, exploring the consequences of this. Then—"We'll meet you in the middle of the city, where we separated." this?" He shook his head angrily, saying, "Judging by reports of the rest of "That would explain why it stopped so suddenly, then." Rodney stood straighter. When he walked again, his steps were firmer. They reached the center of the city, ahead of the small, slight Wass, and stood watching him labor along the metal toward them. might—" Martin shook his head. "No. To be effective, the shield would have to cover the city." Wass stared down at the metal street, as if he could look through it. "I wonder where it gets its power?" plain, and he switched on his flashlight, the other two immediately following his example. The walls and the rounded ceiling of the the streets. There were a multitude of doors and arches set into either side of the corridor. It was rather like ... entering a gigantic metal beehive. roof. "Is this it," Wass murmured, "or an auxiliary?" Martin shrugged. "The whole city's no more than a machine, apparently." "Another assumption," Wass said. "We have done nothing but make assumptions ever since we got here." "The ship leaves in eleven hours." it, get ourselves aboard, and get the big ship away from the planet. "He's right, Rodney. It would be sure death to monkey around in here." halt. "If the dome, or whatever it is, is a radiation screen there must be at least half-a-dozen emergency exits around the city." Rodney said, "To search every building next to the dome clean around the city would take years." Martin nodded. "But there must be central roads beneath this main level leading to them. Up here there are too many roads." leads to another idea. If the band around the city is responsible for a circle. "No supports. No supports anywhere. What keeps all that up there?" "I don't know. I have no idea." Martin gestured toward the ramp with his light. "Does all this, this whole place, look at all familiar to "No, no," Martin answered impatiently, "not just here. I mean the whole city." "Yes," Wass said dryly, "it does. I'm sure this is where all my nightmares stay when they're not on shift." something which could have been anything at all. The metal street ended eventually in a blank metal wall. The edge of the city—the city which was a dome of force above and a bowl of metal below. anything else." They began to retrace their steps along the metal street, back past the same dancing shapes of metal, the partitions, the odd windows, all Martin looked at the metal street lined with its metal objects and he sighed. He remembered how the dark buildings of the city looked at surface level, how the city itself looked when they were landing, and then when they were walking toward it. The dream was gone again for now. Idealism died in him, again and again, yet it was always reborn. But—The only city, so far as anyone knew, on the first planet they'd ever explored. And it had to be like this. Nightmares, Wass said, and Martin thought perhaps the city was built by a race of beings who at some point twisted away from their evolutionary spiral, plagued by a sort of racial insanity. No, Martin thought, shaking his head. No, that couldn't be. of the bank. water." Postpone and postpone until it's too late, and the ship leaves without ourselves and God only knows what else and—" city somewhere." looking back. "It got in and out of the city some way. Perhaps we can leave the same way." "This is different," Wass said. "Built-in traps—" "They had a war," Martin said. Wass agreed. "And the survivors retired here. Why?" it off, Wass. We're looking for reservoirs, you know." "We'll disperse and search carefully," Martin said. "I wonder what the pattern was." "... The reservoirs, Wass. The pattern will still be here for later expeditions to study. So will we if we don't find a way to get out." the same metal as everything else in the city, set beside the disk. The three men, clad in their suits and helmets, grouped around the "Martin! It's all alive! It's moving!" obscuring the dimly seen backdrop of geometrical processions of strange objects. He sighted a path parallel with the avenue above, toward the nearest edge of the city. "I think we'll be all right," he called out, "as long as we avoid the drifts." Rodney stared. "Wass!" he shouted. "We've found a way out!"

<question>:
The crew agrees that the city is

<options>:
A completely dead and worthless for any sort of exploration.
B a machine of some sort.
C full of magical wonders and they must return to the mother ship to let the others know.
D just a typical city.

<answer>:

B