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

<passage>:
Extensive research did not uncover any evidence that the U.S. copyright on this publication was renewed.] The dark star passed, bringing with it eternal night and turning history into incredible myth in a single generation! fifth floor of the opposite apartment, which hereabouts is the floor the pail. Who wouldn't, knowing everyone on Earth was dead except Pa and Ma and Sis and you? Even at that, I don't suppose I should have been surprised. We all huddles back against the blankets hanging around the Nest. Pa says it tick-ticking of the clocks in the Nest and knew I was getting back into air, because there's no sound outside in the vacuum, of course. blankets—Pa's got them faced with aluminum foil to hold in the heat—and came into the Nest. Let me tell you about the Nest. It's low and snug, just room for the four of us and our things. The floor is covered with thick woolly rugs. Three of the sides are blankets, and the blankets roofing it Against one of the blanket-walls is a big set of shelves, with tools The fourth wall has blankets all over except around the fireplace, in which there is a fire that must never go out. It keeps us from freezing and does a lot more besides. One of us must always watch it. Some of the Nest, you could really feel its coldness. It just seemed to suck It slowly melts and vanishes and refreshes the Nest and feeds the fire. The blankets keep it from escaping too fast. Pa'd like to seal the whole place, but he can't—building's too earthquake-twisted, and the first blankets, along with extra coal and cans of food and other through a door to outside. and made a blanket ten feet thick or so everywhere, and then down on stuff mixed in, for it would put you to sleep, maybe for good, and make the fire go out. Next there's the nitrogen, which doesn't count one way or the other, though it's the biggest part of the blanket. On top of that and easy to get at, which is lucky for us, there's the oxygen that keeps us alive. Pa says we live better than kings ever did, breathing All of these gases in neat separate layers. Like a pussy caffay, Pa the entry-slit in the blankets and wringing her hands together—the comes crawling toward the Nest, just like an animal snuffing for outside there, waiting to get us. I've felt it for years—something that's part of the cold and hates all warmth and wants to destroy the Nest. It's been watching us all this time, and now it's coming after him. Habit, I guess, and then there's no denying that this time I was a bit scared. You see, it's this way. We know that everything is dead out there. Pa heard the last radio voices fade away years ago, and had seen some of the last folks die who weren't as lucky or well-protected as us. So we knew that if there was something groping around out there, it couldn't be anything human or friendly. Besides that, there's a feeling that comes with it always being night, cold beyond the orbit of the planet Pluto, Pa says, and taking us farther out all the time. I found myself wondering whether there mightn't be something on the dark star that wanted us, and if that was why it had captured the "You know that game we sometimes play, sitting in a square in the Nest, the Nest and took off our outside clothes, Pa laughed about it all and told them it was nothing and kidded me for having such an imagination, but his words fell flat. He didn't convince Ma and Sis any more than he did me. It looked for a minute like we were all fumbling the courage-ball. Something had to be done, and almost before I knew what I was going to say, I heard myself asking Pa to tell us about the old the shelf and lay it down beside him. nervousness. As if all folks didn't have to hang together and pool every bit of warmth just to keep alive. And how can they have hoped to cross with us once in a while and was probably cross with all those folks. Still, some of the things I read in the old magazines sound pretty wild. He may be right. The dark star, as Pa went on telling it, rushed in pretty fast and there wasn't much time to get ready. At the beginning they tried to keep it a secret from most people, but then the truth came out, what with the earthquakes and floods—imagine, oceans of unfrozen leery of the subject, and he was again tonight. He says he was mostly too busy to notice. You see, Pa and some scientist friends of his had figured out part of airtight walls and doors, and insulation against the cold, and big supplies of food and fuel and water and bottled air. But the place then and in the Big Jerk. So he had to start over and throw the Nest lay his hands on. I guess he's telling pretty much the truth when he says he didn't have any time to keep an eye on how other folks behaved, either then or others clustered around the furnaces in the basements where we go for a leg in splints. In another, a man and woman are huddled together in sitting with a pile of wraps huddled around her, looking hopefully toward the door, as if waiting for someone who never came back with warmth and food. They're all still and stiff as statues, of course, but ever-growing cold, with the temperature creeping down the last few degrees to the last zero, had mysteriously wakened the frozen folk to life—not warm-blooded life, but something icy and horrible? That was a worse idea than the one about something coming down from the dark star to get us. Nest. Pa was telling about the early years in the Nest and had come to the place where he philosophizes. the use of dragging it out for a few years? Why prolong a doomed existence of hard work and cold and loneliness? The human race is done. The Earth is done. Why not give up, I asked myself—and all of a sudden I got the answer." Again I heard the noise, louder this time, a kind of uncertain, enlarge and seal the Nest. I'd do what I could to keep everything survive we'd just thought so, for natural enough reasons. These three found out how a regular little airtight city, with air-locks and all. They even us. One of the men kept saying, "But it's impossible, I tell you. You can't maintain an air supply without hermetic sealing. It's simply go out and shovel the air blanket at the top there was no atmosphere to carry them around the curve of the Earth. Well, they'd found other colonies at Argonne and Brookhaven and way there was something warm down here, so they'd landed to investigate. Of course we hadn't heard them land, since there was no air to carry that they found the Nest a bit smelly, but they never mentioned that at I sort of wished they'd all quit crowding the Nest and let us be alone decided yet just what will happen. Maybe the Nest will be kept up as what one of the strangers called a "survival school." Or maybe we will uranium mines at Great Slave Lake or in the Congo. Of course, now that the strangers are gone, I've been thinking a lot about Los Alamos and those other tremendous colonies. I have a hankering to see them for myself. "It's different, now that we know others are alive," he explains to me. "Your mother doesn't feel so hopeless any more. Neither do I, for that matter, not having to carry the whole responsibility for keeping the human race going, so to speak. It scares a person." I looked around at the blanket walls and the fire and the pails of air light. "It's not going to be easy to leave the Nest," I said, wanting to cry, kind of. "It's so small and there's just the four of us. I get scared with just the Nest. Now it'll be good to have a real huge world again,

<question>:
What is the Nest built inside of?

<options>:
A A train station
B An office building
C It stands alone like a tent
D It’s not known

<answer>:

D