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

<passage>:
Martin crawled into the circular pipe behind the grate. It tilted up Extensive research did not uncover any evidence that the U.S. copyright on this publication was renewed.] Martin set the lifeboat down carefully, with all the attention one usually exercises in a situation where the totally unexpected has occurred, and he and his two companions sat and stared in awed silence was the last thing Martin heard before he collapsed. Martin led Wass, and the gangling, scarecrow-like Rodney, through the Martin looked at the semi-transparent figures of wind and dust slowly across Martin's mind. "All right!" he rapped out—and the image faded. "Sorry," Rodney murmured, his throat working beneath his lantern jaw. Then—"I wonder what it's like here in the winter when there's no light at all?" "I imagine they had illumination of some sort," Martin answered, dryly. "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." "Out there, too, Rodney, they must have had illumination." Martin 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, "Pictures," Martin decided. "We have twelve hours. We'll start here. What's the matter, Wass?" The blond man grinned ruefully. "I left the camera in the lifeboat." There was a pause. Then Wass, defensively—"It's almost as if the city didn't want to be photographed." Martin ignored the remark. "Go get it. Rodney and I will be somewhere Again Martin felt a tug of twisted, distorted familiarity. It was decided to grin at himself, at his own imagination. Martin's spine. "What's the matter?" Anger rose in Martin. "You didn't," he said flatly, gripping the "Martin!" Wass' voice came through the receivers in both their radios. "Martin, I can't get out!" Rodney mumbled something, and Martin told him to shut up. Martin clapped a hand on Rodney's shoulder again, starting him moving, "No go," Martin said to Wass. He bit at his lower lip. "I think it must Walking with Rodney, Martin heard Wass' voice, flat and metallic Martin grinned faintly. Wass, too, had an active imagination. "Well, Wass said coldly, "He's right, Martin." Martin crossed an intersection, Rodney slightly behind him. "You're Martin shrugged. "Let's look." Martin chose an arch, with beyond it a metal ramp, which tilted "What would you suggest, instead?" Martin asked calmly. "No!" Martin said, sharply. That was one assumption they dared not make. "The ship leaves in eleven hours." switch again. Martin swore, stepped forward, pulled him back roughly. thinking of your own tender hide, of course." Rodney cursed. "And every second we stand here doing nothing gives us "I'm holding mine." Martin waited. After a moment, Wass switched his flashlight back on. He said quietly, "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 Wass ignored that, as Martin hoped he would. He said slowly, "That Martin smiled, banishing Wass' idea. Martin shined his light upward, and the others followed his example. Martin turned on his heel and started down a metal avenue which, he Rodney turned swiftly to face him. Martin thought the tall man was holding his gun. "To the switchboard, Martin?" Rodney was holding the gun ... and Wass was.... Then—"I can't think of anything else." Martin was in the lead. Wass followed him silently. Rodney, tall, Martin looked at the metal street lined with its metal objects and he Martin was silent. Wass undertook to explain. Why not, after all? Martin asked himself. It Martin blinked. He thought how little time they had. He wet his lips. Wass' gloved hands fumbled awkwardly at a catch in the nearest section of the bank. Martin thought of the dark, convoluted land outside the city. If they Martin raised his arm tensely. "Opening a seed bank doesn't help us Rodney jerked his head negatively. "No. Now, I know you, Martin. 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—" He reached out convulsively and yanked a switch. Martin leaped, knocking him to the floor. Rodney's gun skittered away silently, like a live thing, out of the range of the torches. "Sorry," Martin said, without feeling. He turned quickly. "Wass?" The slight, blond man stood unmoving. "I'm with you, Martin, but, as Martin was watching Rodney, struggling to get up. "I agree. As a last resort. We still have a little time." Rodney's tall, spare figure looked bowed and tired in the torchlight, now that he was up again. "Martin, I—" Martin turned his back. "Skip it, Rodney," he said gently. Martin glanced at Wass, then started out of the switchboard room, not Martin placed one foot on the metal incline. He angled his torch down, Martin urged him on. "You know what a man-hole cover looks like." He Martin swung his flashlight, illuminating the distorted metal shapes. Their radios recorded Rodney's gasp. Then—"Martin! Martin! I think Martin began to run. After a moment's hesitation, Wass swung in behind From its design Martin assumed that the disk was meant to be grasped Martin kneeled, grasped the wheel. It turned easily—almost too drifted and eddied directly beneath them. Rodney's sudden grip on Martin's wrist nearly shattered the bone. "Martin! It's all alive! It's moving!" Martin hesitated long enough for a coil to move sinuously up toward the opening. Then he spun the wheel and the hatch slammed down. He was shaking. the wind? Air currents are moving it." Rodney sat down on the metal flooring. For a long time he said nothing. Then—"It wasn't.... Why did you close the hatch then?" Martin did not say he thought the other two would have shot him, otherwise. He said merely, "At first I wasn't sure myself." Rodney stood up, backing away from the closed hatch. He held his gun The hatch rose again at Martin's direction. He stood beside it, outlined in the light of two torches. For a little while he was alone. Then—causing a gasp from Wass, a harsh expletive from Rodney—a Martin, sparkling in ten thousand separate particles in the torchlight, Martin raised an arm, and the particles swirled in stately, shimmering nothing. He eyed the sparkling particles swirling about Martin, and Wass sighed and refused to meet Martin's gaze. Martin looked at him disgustedly, and then began to descend the rope, slowly, peering into the infinite, sparkling darkness pressing around him. At the bottom of the rope he sank to his knees in dust, and then was held even. He stamped his feet, and then, as well as he was able, did a standing jump. He sank no farther than his knees. "Of course," Martin growled. Martin pulled his left foot from the sand and growled deep in his Martin. I—" Martin switched off his radio, sick. Rodney's face was white and drawn. "But he did this for us." "So he did," Martin said, very quietly. Then Martin said, "Did you listen until the end?"

<question>:
Why did Martin smile?

<options>:
A He felt amused picturing the aliens crawling everywhere they went
B He felt silly imagining the aliens were man's ancestors
C He felt happy to be exploring the city
D He felt rueful that he left the camera in the lifeboat

<answer>:

B