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

<passage>:
cautious advance of three awed space-scouters. Planet Stories Summer 1955. Extensive research did not uncover any evidence that the U.S. copyright on this publication was renewed.] a city—even a city like this one—in such surroundings. The men from the ship knew only the surface facts about this waiting geometric discovery. Theirs was the eleventh inter-planetary flight, 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 had, an hour ago, with just thirteen hours left during which a return flight could be safely started. So far as was known, this was the only 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 Rodney's bony face was without expression. "Gives me the creeps, kind of. I wonder what they were like?" Wass murmured, "Let us hope they aren't immortal." 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 them, people? Have you noticed how low everything is?" Rodney's laughter rose, too. Then, sobering—"Maybe they crawled." A nebulous image, product of childhood's vivid imagination, moved "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." "Pictures," Martin decided. "We have twelve hours. We'll start here. There was a pause. Then Wass, defensively—"It's almost as if the city didn't want to be photographed." almost as if ... they were human up to a certain point, the point being, perhaps, some part of their minds.... Alien things, dark and subtle, things no man could ever comprehend. Parallel evolution on two inner planets of the same system? Somewhere, it's like a glass wall." "We're trapped, we're trapped, they are—" this?" He shook his head angrily, saying, "Judging by reports of the rest of the planet, it must have been horribly radioactive at one time. All of it." "Man-made radiation, you mean." alien-made, anyhow. Perhaps they had a war." Wass' voice sounded startled. "Anti-radiation screen?" Rodney interrupted, "There hasn't been enough radiation around here for hundreds of thousands of years to activate such a screen." Rodney turned. "But—" "No. Wass, how much time have we?" "The ship leaves in eleven hours." "Eleven hours," Rodney repeated. "Eleven hours!" He reached out for the "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." "Ten hours and forty-five minutes," Wass disagreed softly. "Minus the 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. Martin said, "Not necessarily. You go the way the wind does, always thinking of your own tender hide, of course." Rodney cursed. "And every second we stand here doing nothing gives us that much less time to find a way out. Martin—" 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." "Sure. Why not?" "We're wearing heavy suits and bulky breathing units. We have no equipment." "That shouldn't be hard to come by." to themselves." "Anyway," Martin decided, "we can take a look down below." "Unless someone has a better idea," Martin conceded. He waited. But 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. not?" They were like children.... "We don't know, released, what they'll do." "Skipper," Wass said carefully, "if we don't get out of this place by the deadline we may be eating these." a plant to grow in this environment, it wouldn't need much water. Maybe—" he had a vision of evil plants attacking them, growing with super-swiftness at the air valves and joints of their suits "—only the little moisture in the atmosphere." loud and rather uneven in the radio receivers. Martin made a final effort. "Rodney, it's still almost nine hours to take off. Let's search awhile first. Let this be a last resort." 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. silently, like a live thing, out of the range of the torches. The radio receivers impersonally recorded the grating sounds of resort. We still have a little time." Eleven levels later Rodney asked, "How much time have we now?" "Seven hours," Wass said quietly, "until take-off." 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. the floor. "Martin, what if there are no reservoirs? What if there are cemeteries instead? Or cold storage units? Maybe the switch I pulled—" "Rodney! Stop it!" before the war as a retreat." He turned impatiently. "How should I know?" Wass turned, too, persistent. "But the planet was through with them." "In a minute," Martin said, too irritably, "we'll have a sentient planet." From the corner of his eye he saw Rodney start at that. "Knock it off, Wass. We're looking for reservoirs, you know." They moved slowly down the metal avenue, between the twisted shadow "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." opening. Then he spun the wheel and the hatch slammed down. He was shaking. After a time he said, "Rodney, Wass, it's dust, down there. Remember There was no answer. The light faded swiftly away from the opening. The going was hard. The dust clung like honey to their feet, and eddied 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. without number. Then Wass broke his silence, taunting. "The ship leaves in two hours, Martin. Two hours. Hear me, Rodney?" The grate groaned upward and stopped. Wass babbled incoherently into the radio for a moment, and then he began to scream.

<question>:
The crew has thirteen hours to explore the area. Concerning that time, what do they not always take into account?

<options>:
A They lost an hour when crossing into a different time zone.
B Time on this planet does not occur the same way they are used to.
C They have to take into account getting back to their mother ship and getting it out of the atmosphere during that 13-hour window, as well.
D The planet makes them forget time.

<answer>:

C