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

<passage>:
A Pail of Air By FRITZ LEIBER incredible myth in a single generation! Pa had sent me out to get an extra pail of air. I'd just about scooped it full and most of the warmth had leaked from my fingers when I saw the thing. investigate why the Earth had gone away from the Sun, and maybe to hunt the Sun's protection. of one of the windows to get me. Then I had the wit to go back inside. Pretty soon I was feeling my familiar way through the thirty or so blankets and rugs Pa has got hung around to slow down the escape of into air, because there's no sound outside in the vacuum, of course. But my mind was still crawly and uneasy as I pushed through the last blankets—Pa's got them faced with aluminum foil to hold in the heat—and came into the Nest. 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 touch Pa's head. He tells me it's inside a much bigger room, but I've never seen the real walls or ceiling. Against one of the blanket-walls is a big set of shelves, with tools and books and other stuff, and on top of it a whole row of clocks. Pa's and without a sun or moon, that would be easy to do. which there is a fire that must never go out. It keeps us from freezing the clocks are alarm and we can use them to remind us. In the early of him that way: a tall man sitting cross-legged, frowning anxiously at the fire, his lined face golden in its light, and every so often old days—vestal virgins, he calls them—although there was unfrozen air all around then and you didn't really need one. He was sitting just that way now, though he got up quick to take the her up pretty fast. Sis let off a couple of silly squeals too. Pa handled the pail of air in a twist of cloth. Now that it was inside the Nest, you could really feel its coldness. It just seemed to suck the heat out of everything. Even the flames cringed away from it as Pa Yet it's that glimmery white stuff in the pail that keeps us alive. It slowly melts and vanishes and refreshes the Nest and feeds the through a door to outside. and made a blanket ten feet thick or so everywhere, and then down on blanket sixty or seventy feet thick maybe. or the other, though it's the biggest part of the blanket. On top of pure oxygen, but we're used to it and don't notice. Finally, at the very top, there's a slick of liquid helium, which is funny stuff. All of these gases in neat separate layers. Like a pussy caffay, Pa in, too, but Pa quieted them. We started climbing into our outside clothes—mine had been warming by the fire. Pa made them. They have plastic headpieces that were once big double-duty transparent food cans, but they keep heat and air in and can replace the air for a little while, long enough for our trips for water and coal and food and outside there, waiting to get us. I've felt it for years—something us. It'll get you and then come for me. Don't go, Harry!" Pa had everything on but his helmet. He knelt by the fireplace and reached in and shook the long metal rod that goes up the chimney and on the roof to check if it's working all right. That's our worst trip be anything human or friendly. out all the time. be streets. I sometimes make my mashed potatoes look like it, before I pour on the gravy. Some taller buildings push up out of the feathery plain, topped by rounded caps of air crystals, like the fur hood Ma wears, only of the cold, other icicles of frozen air that melted on the roofs and Inside, he said to me, touching helmets, "If you see something like 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 every bit of warmth just to keep alive. And how can they have hoped to unfrozen Most of the other planets were on the other side of the Sun and didn't get involved. The Sun and the newcomer fought over the Earth for a calls it, when all Earth got yanked suddenly, just as Pa has done to me once or twice, grabbing me by the collar to do it, when I've been 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 what was going to happen—they'd known we'd get captured and our air would freeze—and they'd been working like mad to fix up a place with airtight walls and doors, and insulation against the cold, and big supplies of food and fuel and water and bottled air. But the place got smashed in the last earthquakes and all Pa's friends were killed a leg in splints. In another, a man and woman are huddled together in warmth and food. They're all still and stiff as statues, of course, but just like life. Pa showed them to me once in quick winks of his flashlight, when molecules ought to freeze solid forever? Or like the electricity that from the dark star and making the frozen folk move, using them to do its work. That would fit with both things I'd seen—the beautiful young skin tightened all over me. Pa was telling about the early years in the Nest and had come to the place where he philosophizes. existence of hard work and cold and loneliness? The human race is done. miles from the next planet. And no matter how long the human race might like some rich cloth or fur, or the petals of flowers—you've seen inmost blanket trembled and bulged a little. Just as if they were enlarge and seal the Nest. I'd do what I could to keep everything shoulders—men's faces, white and staring. Well, my heart couldn't have been stopped for more than four or five beats before I realized she was wearing a suit and helmet like Pa's homemade ones, only fancier, and that the men were, too—and that the frozen folk certainly wouldn't be wearing those. Also, I noticed that how they'd survived, Pa let out the biggest whoop of joy. They were from Los Alamos and they were getting their heat and power from atomic energy. Just using the uranium and plutonium intended a regular little airtight city, with air-locks and all. They even generated electric light and grew plants and animals by it. (At this Pa They'd been scouting around for survivors, but they never expected to find any in a place like this. They had rocket ships at Los Alamos and plenty of chemical fuel. As for liquid oxygen, all you had to do was go out and shovel the air blanket at the top level there was no atmosphere to carry them around the curve of the Earth. there was something warm down here, so they'd landed to investigate. dressed at Los Alamos. The strangers marveled at everything and praised it to the skies. I could tell from the way they wrinkled their noses that they found the Nest a bit smelly, but they never mentioned that at all and just asked bushels of questions. In fact, there was so much talking and excitement that Pa forgot about things, and it wasn't until they were all getting groggy that he looked there and I haven't any clothes." hankering to see them for myself. You ask me, Pa wants to see them, too. He's been getting pretty human race going, so to speak. It scares a person."

<question>:
What do humans wear outside on the planet?

<options>:
A They can travel outside without any special gear
B Winter clothes and simple clear helmets
C They never travel outside, only in underground corridors
D Sophisticated astronaut suits from Pa’s old work

<answer>:

B