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

<passage>:
BY RANDALL GARRETT Women on space station assignments shouldn't get pregnant. But there's a first time for everything. Here's the story of such a time——and an historic situation. woman was in pain. There, high in the emptiness of space, Space Station One swung in its orbit. Once every two hours, the artificial satellite looped completely around the planet, watching what went on below. Outside its bright steel hull was the silence of the interplanetary vacuum inside, in the hospital ward, Lieutenant Alice Britton clutched at the sheets of her bed in pain, then relaxed as it faded away. Lieutenant?" she knew the pain wouldn't return for a few minutes yet. "Fine, doctor. It's no worse than I was expecting. How long will The major looked nervously at his wristwatch. "Nearly an hour. You'll Alice Britton closed her eyes. Major Banes was all smiles and cheer "Lieutenant Britton, you're either careless or brainless know which! Your husband may be the finest rocket jockey in the Space Service, but that doesn't give him the right to come blasting up here on a supply rocket just to get you pregnant!" Alice had said: "I'm sure the thought never entered his mind, doctor. I "I didn't know," she had said stolidly. "You know my medical record." not equipped for obstetrics up here." And he had looked up at her scathingly. "Lieutenant Britton, it is She hadn't thought of it before, but the major was right. The terrible punishment for long, much less the tiny life that was growing within her. So she had stayed on in the Space Station, doing her job as always. As Chief Radar Technician, she was important in the operation of the station. Her pregnancy had never made her uncomfortable the slow rotation of the wheel-shaped station about its axis gave an effective According to the major, the baby was due sometime around the first of you shouldn't weigh more than seventy pounds then. You're to report to me at least once a week, Lieutenant." As the words went through her mind, another spasm of pain hit her, and she clenched her fists tightly on the sheets again. It went away, and Everything had been fine until today. And then, only half an hour ago, space. The depressurization hadn't hurt her too much, but the shock had been enough to start labor. The baby was going to come two months early. She relaxed a little more, waiting for the next pain. There was nothing she had absolute faith in the red-haired major. The Chief Nurse at a nearby desk took off her glasses and looked at him speculatively. "Something wrong, doctor?" "Incubator," he said, without taking his eyes off the clock. "I beg your pardon?" "Incubator. We can't deliver a seven-month preemie without an incubator." The nurse's eyes widened. "Good Lord! I never thought of that! What are I'll ask them to send up an emergency rocket with an incubator. But—" "But what?" "Will we have time? The pains are coming pretty fast now. It will be at least three hours before they can get a ship up here. If they miss us on the next time around, it'll be five hours. She can't hold out that long." wall clock. She could feel a lump in her throat. Major Banes was in the Communications Center a full five minutes impatiently as he waited for the answer. He turned and left through the heavy door. Each room of the space station was protected by airtight doors and individual heating units if some accident, such as a really large meteor hit, should release the Alice Britton was resting quietly, but there were lines of strain "How's it coming, Lieutenant?" He forced a nervous smile. "Nothing but the responsibility. You're going to be a very famous woman, you know. You'll be the mother of the first child born in space. And it's my job to see to it that you're both all right." Colonel Gates, the O.B. man, was supposed to come up for the delivery kept wandering to his wristwatch, timing Alice's pain intervals. They the Chief Nurse. "There's a message for you in your office, doctor. THE FORT, BABY, THE WHOLE WORLD IS PRAYING FOR YOU. OUT. Banes sat on the edge of his desk, pounding a fist into the palm of his left hand. "Two hours. It isn't soon enough. She'll never hold out that long. And we don't have an incubator." His voice was a clipped monotone, timed with the rhythmic slamming of his fist. The Chief Nurse said: "Can't we build something that will do until the looks as though the Space Service has released the information to the public. Lieutenant Britton's husband was right when he said the whole the Chief Nurse's eyes. "They've released the news to the public." She frowned. "That really puts you on the spot. If the baby dies, "Yes, sir. I just thought—" save that baby!" He paused as he saw her eyes. "I'm sorry, Lieutenant. My nerves are all raw, I guess. But, dammit, my field is space medicine. I can handle depressurization, space sickness, and things like that, but I don't know anything about babies! I know what I read know. I don't even have any references up here people aren't supposed to go around having babies on a space station!" "It's all right, doctor. Shall I prepare the delivery room?" His laugh was hard and short. "Delivery room! I wish to Heaven we had one! Prepare the ward room next to the one she's in now, I guess. It's The nurse left quietly. She knew Banes wasn't really angry at the it was simply his way of letting off steam to ease the smoke to calm his raw nerves, but it was strictly against regulations. in space. The air purifiers in the hydroponics section could keep the air fresh enough for breathing, but fire of any kind would overtax the system, leaving too little oxygen in the atmosphere. wasn't getting much read. She dropped it to the floor when he came in. "Nothing serious. I just want to make sure everything comes out all months ago. Or did you forget something?" That hit home, but he just grinned feebly. "I forgot to get somebody to that keeps him out of the way, and the doctor has coffee Alice's hands grasped the sheet again, and Banes glanced at his watch. "I'll say it won't! How about the incubator?" There was a long pause. Finally, he said softly: "There isn't any incubator. I didn't take the possibility of a premature delivery into bringing one up. I—I think we'll be able to keep the child alive "Lieutenant! Lieutenant Britton! Alice! This is no time to get He blinked. "What do you mean?" Another pain came, and he had to wait until it was over before he got her answer. "Doctor," she said, "I thought you would have figured it out. Ask yourself just one question. Ask yourself, 'Why is a space station like an incubator?'" Space Ship Twelve docked at Space Station One at exactly eleven thirty-four, and two men in spacesuits pushed a large, bulky package through the airlock. ?" The colonel said nothing, but he raised an eyebrow. "But—but—the incubator—" Banes' grin widened. "We'll put the baby in it, now that we've got it, but it really isn't necessary. Your wife figured that one out. A space station is a kind of incubator itself, you see. It protects us poor, weak humans from the terrible conditions of space. So all we had to do was close up one of the airtight rooms, sterilize it, warm it up, and "Don't thank me. It was Captain Britton's wife who—"

<question>:
Why didn't the Lieutenant know she was pregnant?

<options>:
A She has an irregular cycle.
B She had her tubes tied before going into space.
C She wasn't keeping track of her cycle.
D Women don't have periods in space.

<answer>:

A