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

<passage>:
new air units now. There was a time when we had to be very careful to spend two years there." that psychologists and research men agree that research stations should be staffed by couples. That is, of course, as soon as it's practical." "But that might be a long time!" the very young man protested. "It might be—but sometimes it's sooner than you think. And the goal is worth it." "I suppose so, but—" Three years on the Moon and they didn't want him to come back. Three years on the Moon and they thought he'd be glad to stay for more. Just raise his salary or give him a bonus, the every-man-has-his-price idea. They probably thought he liked it there. only ten steps in any one direction. Their little scientific home of year and a half. Or maybe three. He should probably be glad he had the opportunity. The key started to stutter again, demanding an answer. He tapped out his reply: " No! " "Well, don't let it throw you. They've never been here on the Moon. man to stay on the job a while longer." " All they're trying to do," Chapman said sarcastically. "They've got a fat chance." "They think you've found a home here," Donley said. for breakfast duty. The others started lacing up their bunks, getting ready for their last day of work on the Moon. In a few hours they'd be relieved by members small condensed milk tins slid over crossed iron bars. You could still see the footprints in the powdery soil where the group had gathered about the grave. It had been more than eighteen months ago, but there was no wind to wear those tracks away. They'd be there forever. That's what happened to guys like Dixon, Chapman thought. On the Moon, left there twelve hours ago. They should get here"—he looked at his watch—"in about six and a half hours." "Chap, you know, I've been thinking," Donley said quietly. "You've been here just twice as long as the rest of us. What's the first thing you're going to do once you get back?" It hit them, then. Dowden and Bening looked blank for a minute and have waited so long for Christmas that they just can't believe it when it's finally Christmas Eve." have, but I think I know what you mean." He warmed up to it as the idea sank in. "Just what the hell are Chapman grinned. "Oh, just somebody. What are you going to do, Dick?" "Well, I'm going to do something practical. First of all, I want to turn over all my geological samples to the government. Then I'm going to sell my life story to the movies and then—why, then, I think I'll get drunk!" to the expedition. Then I think I'll go home and see my wife." They were quiet. "I thought all members of the groups were supposed to be single," Donley said. "They are. And I can see their reasons for it. But who could pass up the money the Commission was paying?" "If I had to do it all over again? Me," said Donley promptly. too much. The party quieted down after a while and Dowden and Bening finished leaks," he warned. "And check the valves of your oxygen tanks." Donley looked sour. "I've gone out at least five hundred times," he said, "and you check me each time." "And I'd check you five hundred more," Chapman said. "It takes only one mistake. And watch out for blisters under the pumice crust. You go through one of those and that's it, brother." of people. Bad people and good people and fat people and thin people, and people I can't understand. People who wouldn't know an atom from an artichoke. And people who wouldn't give a damn. We're a quarter of a million miles from nowhere, Julius, and to make it literary, I think I miss my fellow man more than anything." Being on the Moon was the opportunity of a lifetime. He thought so much themselves. The Moon's a new environment and you have to learn how to machinery. When it occurred to us that somebody was going to have to stay over, I volunteered. I thought the others were so important that it was better they should take their samples and data back to Earth it's somebody else's turn now. He volunteered for it. I think I was fair in explaining all about the job when you talked it over among yourselves." His voice trailed away. "It's just that I think it's such a damn important job." Klein had gone out in a last search for rock lichens and Chapman bag was already packed and had been for a week. He remembered stalling it off for as long as he could and then the quiet satisfaction about a week before, when he had opened his small gear locker and transferred its meager belongings to the bag. He hadn't actually needed to pack, of course. In less than twenty-four hours he'd be back on Earth where he could drown himself in toothpaste and buy more tee shirts than he could wear in a lifetime. He could probably use them or maybe one of the boys in the Third. But it wasn't like going home unless you packed. It was part of the ritual, like marking off the last three weeks in pencil on the gray to the Moon. sweat and his eyes were frightened. He moistened his lips slightly. "Do—do you think they'll ever have relief ships up here more often than every eighteen months, Chap? I mean, considering the advance of—" "No," Chapman interrupted bluntly. "I don't. Not at least for ten years. The fuel's too expensive and the trip's too hazardous. On freight charges alone you're worth your weight in platinum when they so it will shorten stopover right away." He stopped, feeling a little sorry for Dahl. "It won't be too bad. There'll be new men up here and than you do," Chapman said slowly. "I may have commitments at home, too. What made you think I would change my mind?" to remember such a thing as pride, "you know my father's pretty well fixed. We would make it worth your while, Chap." He was feverish. "It would mean eighteen more months, Chap, but they'd be well-paid months!" Chapman felt tired. The good feeling he had about going home was slowly evaporating. "If you have any report to make, I think you had better get at it," group had been when they had landed. Like Chapman had been in the First. Donley and the others were all over them. turn color in the autumn, did people still love and cry and were there still people who didn't know what an atom was and didn't give a damn? Chapman had gone through it all before. But was Ginny still Ginny? Some of the men in the Third had their luggage with them. One of them—a husky, red-faced kid named Williams—was opening a box about a smuggle something like that up to the Moon instead of his phonograph. "That's valuable grass," Dahl said sharply. "Do you realize that at current freight rates up here, it's worth about ten dollars a blade?" Williams looked stricken and somebody said, "Oh, shut up, Dahl." One of the men separated from the group and came over to Chapman. He plans for the station," he said. "I hadn't heard of them." "Oh, yes, big plans . They're working on unmanned, open-side rockets now that could carry cargo and sheet steel for more bunkers like this. Enable us to enlarge the unit, have a series of bunkers all linked together. Make good laboratories and living quarters for you people." "Is that all?" Eberlein was ill at ease. "Naturally you'd be paid well. I don't double your salary—maybe even a bonus in addition—and let you have full charge. You'd be Director of the Luna Laboratories." All this and a title too, Chapman thought. "That's it?" Chapman asked. Eberlein frowned. "Well, the Commission said they'd be willing to consider anything else you had in mind, if it was more money or...."

<question>:
How many people live on the moon at any one time?

<options>:
A People are coming and going all the time
B About a dozen
C About half a dozen
D Several dozen

<answer>:

C