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

<passage>:
toward the surface. "Come on, Rodney. Last lap." cautious advance of three awed space-scouters. An hour later they surfaced about two hundred yards away from the Ahead of them were the other two scoutships from the mother ship. standing by the scoutships, and at the edge of the city, began to run Martin set the lifeboat down carefully, with all the attention one Wass, blond and slight, with enough nose for three or four men, unbuckled his safety belt and stood up. "Shall we, gentlemen?" and with a graceful movement of hand and arm he indicated the waiting city. 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 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 Wass murmured, "Let us hope they aren't immortal." Martin stood up. "Let's try farther on. Rodney, radio the ship, tell 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. "If we don't hurry up and get through this place and back to the ship, we're very likely to find out." Rodney said quickly, "I mean outside." 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, The blond man grinned ruefully. "I left the camera in the lifeboat." "We're trapped, we're trapped, they are—" "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." "Why not?" 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." 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?" "Down below, probably. If there is a down below." Martin hesitated. "We may have to...." 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 corridor were of the same dull metal as the buildings' facades, and 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. looks like a switchboard." The three advanced to the end of the central corridor, pausing before a "Is this it," Wass murmured, "or an auxiliary?" "What would you suggest, instead?" Martin asked calmly. "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 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. And Captain Morgan can't wait for us, Martin." Rodney cursed. "And every second we stand here doing nothing gives us "Make one move toward that switchboard and I'll stop you where you "He's right, Rodney. It would be sure death to monkey around in here." "Well...." Rodney turned quickly toward the black arch. "Let's get out Martin hung back waiting for the others to go ahead of him down the metal hall. At the other arch, where the ramp led downward, he called a 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." "Have you a better idea?" the dome, does it project down into the ground as well?" "You mean dig out?" Martin asked. "Sure. Why not?" "We're wearing heavy suits and bulky breathing units. We have no "Anyway," Martin decided, "we can take a look down below." city." "Yes," Wass said dryly, "it does. I'm sure this is where all my thought, paralleled the street above. And Rodney and Wass followed him "We go back, I guess," Martin said. "Unless someone has a better idea," Martin conceded. He waited. But anything else." They began to retrace their steps along the metal street, back past some point twisted away from their evolutionary spiral, plagued by a "Skipper," Wass said carefully, "if we don't get out of this place by 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 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 ourselves and God only knows what else and—" "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. Wass agreed. "And the survivors retired here. Why?" before the war as a retreat." He turned impatiently. "How should I Wass turned, too, persistent. "But the planet was through with them." 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. "We'll disperse and search carefully," Martin said. expeditions to study. So will we if we don't find a way to get out." "Well, Skipper, are you going to do the honors?" hinge. The three men, clad in their suits and helmets, grouped around the six-foot opening, shining their torches down into the thing that drifted and eddied directly beneath them. Then—"It wasn't.... Why did you close the hatch then?" tenuous, questing alien limb edged through the hatch, curling about of the hatch to stare coldly at Wass. "You'd rather monkey with the switches and blow yourself to smithereens?" 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." "Not me," the answer came back quickly. "You two fools go your way, I'll go mine." "Are we going straight?" Rodney asked. Then Wass broke his silence, taunting. "The ship leaves in two hours, Rodney stared. "Wass!" he shouted. "We've found a way out!"

<question>:
Running out of options, the crew decides to follow

<options>:
A Their heart.
B The map.
C Their instincts.
D The passage where water enters and exits the city.

<answer>:

D