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

<passage>:
machine out there too long—until you get used to it, you'll find it's to it, of course, but it will take about thirty years. how you feel for half an hour or so, until you get over it. After that you'll come I'll be tired of talking by then, and in a hurry to get going. So I foggy nothing surrounding the cockpit prevents passage through time from affecting us. The luggage section and everything outside will disappear. You look for your house, but and you don't try it again. Then it comes to you slowly that you're actually traveling in time. "Not exactly," I try to explain. "Maybe it's no dimension—or it might the machine and I don't understand it." then the time-machine. And when you closed the loop by going back and bent back on itself. Maybe there is no machine, and it's just easier apparently, though there is a time effect back in the luggage space. increment of time from the main field. I don't know, and you won't think about that then, either. I'm smoking, and so are you, and the air in the machine is getting a bit stale. You suddenly realize that everything in the machine is wide open, yet you haven't seen any effects of air loss. "Where are we getting our air?" you ask. "Or why don't we lose it?" "No place for it to go," I explain. There isn't. Out there is neither time nor space, apparently. How could the air leak out? You still feel gravity, but I can't explain that, either. Maybe the machine has a Then the machine stops—at least, the field around us cuts off. You feel a dankish sort of air replace the stale air, and you breathe easier, though we're in complete darkness, except for the weak light in the machine, which always burns, and a few feet of rough dirty cement floor around. You take another cigaret from me and you get out of the machine, just as I do. of simple, short-limbed, one-piece affair I put on, but it feels comfortable. "I'm staying here," I tell you. "This is like the things they wear in back with you." "What about the time machine?" you ask. "Since nobody ever stole it, it's safe." We get in the elevator, and I say "first" to it. It gives out a coughing noise and the basement openings begin to click by us. There's no feeling of acceleration—some kind of false gravity they use in the future. Then the door opens, and the elevator says "first" back at us. It's obviously a service elevator and we're in a dim corridor, with passengers moving up a ramp, and the office is closed. You begin to get lower than they used to, apparently. Twenty floors up seems about the You go up the steps, but you see that it seems to be closed. You is complete nonsense, and you should get back to the time machine and go home. But then a guard comes to the gate. Except for the short legs of drawl, with softer vowels and slurred consonants, but it's rather obviously he isn't locking it. In fact, there doesn't seem to be a lock. "Must be a new part. You go down that corridor, up one flight You get away from him, finally, after some polite thanks. The building goes through a crazy wiggle inside, stops turning out a continual row "Souvenir," it announces in a well-modulated voice. "This is a typical You put it in your pocket, gulping a little, and get back to the fact that they have the original model of the first atomic generator They state that it has all major refinements, operating on any fuel, fifty kilowatts, limited by the current-carrying capacity of the outputs. They also mention that the operating principle is still being . Apparently that's the way it's fueled. It's about one foot on "Nice," the guard says over your shoulder. "It finally wore out one of the cathogrids and we had to replace that, but otherwise it's exactly as the great inventor made it. And it still operates as well as ever. arriving, but I'll be back in about ten minutes. He wants to examine thing is absolutely fixed. You can't see any bolts, but you can't budge probably bolted down, too, but you try it tentatively and you find it it, since the gravostatic plate is being renewed. it only weighs about fifty pounds! Naturally, it can be probably can't help it, anyhow. Pre-set, you might say. You stumble down the stairs, feeling all the futuristic rays in the is closed. You reach it and it opens obligingly by itself. You breathe Then there's a yell behind you. You don't wait. You put one leg in of your feet, with a sudden ringing sound. You don't wait to find out seeming to come out of the sockets, and that atomic generator getting heavier at every step. "You can't exert yourself that hard in this heat, fellow," the cop Reaction sets in a bit and your knees begin to buckle, but you shake your head and come up for air. dissimilar in other ways. He snaps it open and you get set to duck. You swallow several sets of tonsils you had removed years before, and to satisfy your amiable guard friend. He finally smiles in satisfaction and heads back to the museum. You still don't believe it, but you pick up the atomic generator and the information sheets, and you head down toward the service elevator. There is no button on it. In fact, there's no door there. You start looking for other doors or corridors, but you know this is right. The signs along the halls are the same as they were. Then there's a sort of cough and something dilates in the wall. It gulping out something about going all the way down, and then wonder how closed and is moving downward in a hurry. It coughs again and you're at You'll never know what you stumbled over, but, somehow, you move back in the direction of the time machine, bumping against boxes, staggering it's the weak light in the time machine. You've located it. You put the atomic generator in the luggage space, throw the papers down beside it, and climb into the cockpit, sweating and mumbling. You reach forward toward the green button and hesitate. There's a red one It isn't much of a trip back. You sit there smoking and letting your nerves settle back to normal. You notice a third set of buttons, with some pencil marks over them—"Press these to return to yourself 30 years"—and you begin waiting for the air to get stale. It doesn't because there is only one of you this time. Instead, everything flashes off and you're sitting in the machine in your own back yard. You'll figure out the cycle in more details later. You get into the land in your back yard, and then hop back thirty years to pick up generator and taking it inside. It isn't hard to disassemble, but you don't learn a thing But when you put it together again, about an hour later, you notice Everything in it is brand-new and there's one set of copper wires the set on the other side, drop in some iron filings, and try it again. And with the controls set at 120 volts, 60 cycles and 15 amperes, you feel a little happier when you realize that the luggage space wasn't insulated from time effects by a field, so the motor has moved backward in time, somehow, and is back to its original youth—minus the replaced wires the guard mentioned—which probably wore out because of But you begin getting more of a jolt when you find that the papers are Before long, your riches from the generator are piling in. Little that's waiting in the building you had put around it. Then you'll be came looking for you and shouting, before the time machine left.

<question>:
Why is the air inside the machine not stale on the return trip like it had been on the prior trip?

<options>:
A Because the generator is working and clearing the air.
B Because there is a clearer air flow now with the retrieval of the generator.
C Because no one is smoking inside the machine.
D Because there is only one Jerome smoking inside the machine.

<answer>:

D