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

<passage>:
spaceship—and nothing could ever stop her now. Not unless she broke down completely in front of all these hurrying, Moon-bound passengers, in plain sight of the scattered crowd which clustered on the other waist. It was like a benediction. "He'll be born on the Moon," he whispered, "and he'll have eyes the color of all Earth when it looks out to the stars." " She'll be born on the Moon," corrected Marcia, "and her name will be Sue, and ... and she'll be almost as good as her father." Avoiding It May Cost Your Life! to realize how dangerous that is." her lip. Silly ... Jack had said that—her fear of space was silly. He'd said it during the quarrel, and he'd roared at her, "And that's why you want me to come back—ground myself, be an Earth-lubber—so I ! It's been nineteen whole years since your father died in the explosion of a Moon-rocket. Rocket motors just don't explode any more, honey! Ships travel to the Moon and back on iron-clad, mathematical orbits that are figured before the ship puffs a jet—" "The Elsinore Everyone knew about the Elsinore , the 500-foot Moon-ferry that almost missed the Moon. "That," he said bitterly, "was human damnfoolishness botching up the equations. Too many lobbyists have holdings on the Moon and don't who never realizes that certain glandular conditions are fatal in free reached the free-fall flight, where power could be shut off, the skipper had to put the ferry into an axial spin under power, creating artificial gravity to save the worthless life of that fool. So of course he lost his trajectory, and had to warp her in as best he could, without passing the Moon or crashing into it. And of course you're not listening." "It's all so dull!" she had flared, and then, "How can I be interested Jack. Or even to the Moon.... Sitting rigid in the tense stillness of a rocket ship that was about to leap from Earth, Marcia started as an officer ducked his head into the passenger compartment from the pilot room's deep glow. But it "Those of you who haven't been in a rocket before won't find it much had grown around the ship, Earth was a mystic circle, a shallow dish floating darkly and heavily below. "We are now," said Miss Eagen's calm voice, "thirty-seven miles over Los Angeles." After that, there was scarcely room for thought—even for fear, though it lurked nearby, ready to leap. There was the ascent, the quiet, sleeplike ascent into space. Marcia very nearly forgot to breathe. She had been prepared for almost anything except this quality of peace and awe. started, and do it right now, this minute. It might already be too late ... she wished, suddenly, and for the very first time, that she'd paid more attention to Jack's ramblings about orbits and turn-over Marcia's shoulder. "Just a touch of space-sickness. This way. That's it. We'll have you fixed up in a jiffy." "It isn't s-space sickness," said Marcia in a very small and very "Why, what—is there to be scared of?" out! She looked at the trim girl with hating eyes. The intercom said, "You know I've got course-correction computations from here to yonder. passengers that there won't be any free fall. Most of them are looking spin, that outside bulkhead is going to be down . Centrifugal force, see?" And before she could answer him he added, "I can't talk and work She sighed. "It's well known—even by you—that the free-fall condition has a weird effect on certain people. The human body is in an unprecedented situation in free fall. Biologically it has experienced swimming. Free-fall means that everything around you is 'up.' The body's reactions to free-fall go much deeper than space-nausea and a mild feeling of panic. When there's a glandular imbalance of certain the 17-kesteroids begin spastic secretions the—well, it varies in individuals. But it's pretty well established that the results can be fatal. It kills men with prostate trouble—sometimes. It kills women in menopause—often. It kills women in the early stages of pregnancy— "Convulsions. A battle royal between a glandular-level panic and a Muscles tear, working against one another. Lungs rupture and air is forced into the blood-stream, causing embolism and death. Not especially susceptible because their protective reflexes, through and "And the only thing that can be done about it is to supply gravity?" "Or centrifugal force (or centripetal, depending on where you're standing, but why be technical?)—or, better yet, keep those people off the ships." with the same force as gravity, and then everything will be all right." "You make it sound so simple." minute he's working over the computer—a small, simple, ship-board computer—working out orbital and positional and blast-intensity data that would be a hard nut for the giant calculators on Earth to crack. And he's doing it in half the time—or less—than it would take the because it's a life-and-death the same way he does when it isn't?" Through a growing fear, Marcia nodded mutely. "He'll spin the ship on its long axis," said the stewardess with exaggerated patience. "That means that the steering jet tubes in the nose and tail are spinning, too. You don't just turn with a blast on slight course correction. The sighting instruments are wheeling round and round while you're checking your position. Your fuel has to be calculated to the last ounce—because enough fuel for a Moon flight, with hours of fuelless free-fall, and enough fuel for a power spin and course corrections while spinning, are two very different things. Captain McHenry won't be able to maneuver to a landing on the Moon. He'll do it exactly right the first time, or not at all." Marcia was white and still. "I—I never—" "But I haven't told you the toughest part of it yet," Miss Eagen went on inexorably. "A ship as massive as this, spinning on its long axis, is a pretty fair gyroscope. It doesn't want to turn. Any force that position and away again, the firing formulas get—well, complex. And the ship's course and landing approach are completely new. Instead of letting the ship fall to the Moon, turning over and approaching tail-first with the main jets as brakes, Captain McHenry is going to have to start the spin first and go almost the whole way nose-first. He'll come up on the Moon obliquely, pass it, stop the spin, turn over once to check the speed of the ship, and once again to put the tail down when the Moon's gravity begins to draw us in. There'll be two short periods of free-fall there, but they won't be long enough to bother you much. And if we can do all that with the fuel we've got, it Marcia forced herself away from the bulkhead with a small whimper of hurt and hatred—hatred of the stars, of this knowledgeable, inspired "Where are you going?" Moon's disc. Next to it, and below, was the rear viewer, holding the shimmering azure shape of Earth. " All Earth watches me when I work, but with your eyes. " There was a sudden thunder. Over Miss Eagen's shoulder, through the port, Marcia saw the stars begin to move. Miss Eagen followed her gaze. "He's started the spin. You'll be all right now." But through and through that drugged, relaxed period, Jack and the stars, the Moon and Sue Eagen danced and wove. Words slipped in and out of it like shreds of melody: disintegrate, and someone kept saying, "Hold tight, Marcia hold tight

<question>:
For humans, what is the most dangerous part of the trip to the moon?

<options>:
A Freefall
B Take off
C Landing
D Orbit

<answer>:

A