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

<passage>:
DUST UNTO DUST Martin crawled into the circular pipe behind the grate. It tilted up toward the surface. "Come on, Rodney. Last lap." An hour later they surfaced about two hundred yards away from the Ahead of them were the other two scoutships from the mother ship. Martin called out faintly, pulling Rodney out of the pipe. Crew members standing by the scoutships, and at the edge of the city, began to run toward them. unbuckled his safety belt and stood up. "Shall we, gentlemen?" and with a graceful movement of hand and arm he indicated the waiting city. Martin led Wass, and the gangling, scarecrow-like Rodney, through the stillness overlaying the barren ground. There was only the twilight The men from the ship knew only the surface facts about this waiting and the previous ten, in the time allowed them for exploration while this planet was still close enough to their own to permit a safe return flight could be safely started. So far as was known, this was the only them we're going in." 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." "Could be," Martin said. "Let's go in." 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 "If we don't hurry up and get through this place and back to the ship, we're very likely to find out." 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 explained most of it ... most of it. But he felt the black city was along this street." Wass turned away. Martin and Rodney started slowly down the wide metal from the other direction." "We're trapped, we're trapped, they are—" Martin clapped a hand on Rodney's shoulder again, starting him moving, toward the city's edge, past the black, silent buildings. 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." 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. Wass' face, Martin saw, was sober. "I tried to call the ship. No luck." "I wonder where it gets its power?" "What?" Rodney prompted. Martin shrugged. "Let's look." He led the way through a shoulder-high arch in one of the tall buildings surrounding the square. The corridor inside was dim and Martin chose an arch, with beyond it a metal ramp, which tilted downward, gleaming in the pale circle of his torch. looks like a switchboard." The three advanced to the end of the central corridor, pausing before a great arch, outlined in the too-careful geometrical figures Martin had come to associate with the city builders. The three torches, shining "The ship leaves in eleven hours." "We have to find out what all this stuff's for!" "Going at it blindly, we'd probably execute ourselves." "We've got to—" "No!" Then, more quietly—"We still have eleven hours to find a way out." time it takes us to get to the lifeboat, fly to the ship, land, stow it, get ourselves aboard, and get the big ship away from the planet. "You too, Wass?" "Up to the point of accuracy, yes." Martin said, "Not necessarily. You go the way the wind does, always thinking of your own tender hide, of course." "Make one move toward that switchboard and I'll stop you where you "Well...." Rodney turned quickly toward the black arch. "Let's get out of here, then!" Martin hung back waiting for the others to go ahead of him down the leading to them. Up here there are too many roads." "Have you a better idea?" "You mean to themselves." darkness before the men. At length the incline melted smoothly into the next level of the city. Martin shined his light upward, and the others followed his example. on them. Wass turned his light parallel with the floor, and then moved slowly in Martin turned on his heel and started down a metal avenue which, he thought, paralleled the street above. And Rodney and Wass followed him silently. They moved along the metal, past unfamiliar shapes made more so by gloom and moving shadows, past doors dancing grotesquely in the past something which was perhaps a conveyor belt, past another 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 looking different now in the new angles of illumination. Martin was in the lead. Wass followed him silently. Rodney, tall, matchstick thin, even in his cumbersome suit, swayed with jaunty some point twisted away from their evolutionary spiral, plagued by a They were like children.... "We don't know, released, what they'll do." find a way out of here." He started up the ramp. "Besides, we've no water." Rodney came last up the ramp, less jaunty now, but still holding the gun. His mind, too, was taken up with childhood's imaginings. "For a plant to grow in this environment, it wouldn't need much water. take off. Let's search awhile first. Let this be a last resort." Postpone and postpone until it's too late, and the ship leaves without us and we're stranded here to eat seeds and gradually dehydrate a last resort it might be better to be blown sky high than to die now that he was up again. "Martin, I—" Martin turned his back. "Skip it, Rodney," he said gently. "Water," Wass said thoughtfully. "There must be reservoirs under this city somewhere." Rodney said, "How does water help us get out?" Martin glanced at Wass, then started out of the switchboard room, not looking back. "It got in and out of the city some way. Perhaps we can leave the same way." Down the ramp again. think it's the last." They walked down the ramp and stood together, silent in a dim pool of artificial light on the bottom level of the alien city. before the war as a retreat." He turned impatiently. "How should I it off, Wass. We're looking for reservoirs, you know." They moved slowly down the metal avenue, between the twisted shadow shapes, looking carefully about them. added dryly, "Use your imagination." They reached the metal wall at the end of the avenue and paused again, uncertain. "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." six-foot opening, shining their torches down into the thing that the wind? Air currents are moving it." tenuous, questing alien limb edged through the hatch, curling about spirals. switches and blow yourself to smithereens?" the infinite, sparkling darkness pressing around him. At the bottom stamped his feet, and then, as well as he was able, did a standing jump. He sank no farther than his knees. 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." I'll go mine." and swirled about them until the purifying systems in their suits were hard-pressed to remove the fine stuff working in at joints and valves. "Are we going straight?" Rodney asked. plunged forward, to sink again to the knees, repeated the act, times without number.

<question>:
What is ultimately their way to freedom?

<options>:
A Their souls were set free when they all died on the planet.
B Eating the seedpods transported them back to their ship.
C Wass sacrificed himself by using the switchboard, which released the others.
D Following the route of the water.

<answer>:

C