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

<passage>:
Rootless and footloose, a man in space can't help but dream of coming home. But something nobody should do is bet on the validity of a homesick dream! A murmur greeted the order. Craig experienced the thrill of knowing the envy of the others. Grav 1—that meant Terra. He crossed the long, dreary room, knowing the eyes of the other men were upon him. tapes was known as far into space as lonely men had penetrated. Intergalactic considered them as great a menace to mental and moral stability as the hectopiates. Craig wearily got the man out of the room, took a PON pill, and eased himself into the bed. It had been a weird day and he had not liked it. There was no telling how long it would take him to shake his—sea legs, the psychologist had called it. One thing was sure: Terra aggressively went after its strangers. that he had missed an important step in the complicated clerical process. He cursed the grudging attitude of the headquarters satellite personnel and felt the impotence of a spaceman who had long forgotten Craig obeyed the robot voice and began reluctantly to remove his flight jacket. Its incredibly fine-grained leather would carry none of the to your orders." Craig quickly removed the last of his clothing. It was impossible to hate a robot, but one could certainly hate those who set it into "I'm a little anxious to get home, I suppose," said Craig defensively. "By 'home' you mean Terra. But you've never been there, have you?" "No, but my father—" "I was entered as a spaceman when I was 16," Craig said. "I've never been down for any period as yet." "You mean you haven't been in a gravity system?" "Oh, I've landed a few times, even walked around for a while...." "With the help of paraoxylnebutal," supplied the captain. The captain laughed reassuringly. "No, don't put up your guard again. The worst is over. Short of Gravitational conditioning, there is nothing to stop you from going to Terra." "Sorry, I guess I'm a little touchy. This is my first time...." "Quite natural. But it being your first time—in quite a number of conditioning." "Conditioning?" asked Craig. "Yes. You have spent eleven years in space. Your body is conditioned to a normal state of free fall, or at best to a state of acceleration." "Yeah, I know. Once on Gerymeade...." "You were ill, couldn't keep your balance, felt dizzy. That is why all spacemen carry PON, paraoxylnebutal, with them. It helps suppress certain physiological reactions to an entirely new set of conditions. Channels of the ear, for example. They play an important function. Returning to gravity is rather frightening at first." "I know all about this, Captain." "You've undoubtedly read popularizations in tapezines. But you have wordy psychologist. What was the man actually saying? During the days that followed, the psychologist seemed to Craig to about the "freedom of open space." He spoke repetitiously of the "growing complexity of Terran society." And yet the man could not be pinned down to any specific condition the spaceman would find intolerable. Craig began to hate the delay that kept him from Terra. Through the space. They were incredibly varied, even those that supported life. He had weathered difficult landings on worlds with rip-tide gravities, had felt the pull of the incredible star-tides imparted by twin and even triple star systems. He had been on Einstein IV, the planet of eight unspoken warning he felt underlying all that the man said. gave you my reasons for quitting space. We analyzed them. You agreed that you could not decide that for me and that my decision is logical. You tell me spacemen don't settle down on Terra. Yet you won't—or can't—tell me why. I've got a damned good job there—" "You may find that 'damned good jobs' become boring." "Mr. Craig," the psychologist said slowly, "you have my authorization definitely need. Good luck. You'll need that too." On the eighth day, two attendants, who showed the effects of massive doses of PON to protect themselves from the centrifugal force, had to carry a man out of the tank. Many others asked to be removed, begged to be allowed to withdraw their resignations. "The twelfth day is the worst," a grizzled spaceman told Craig. "That's when the best of 'em want out." Craig clenched the iron rung of his bed and struggled to bring the old "Can't they ... drop it down continuously?" "They tried that a few times—once when I was aboard. You wouldn't like it, kid. You wouldn't like it at all." upon wave of nausea swept him as he watched the seam lines bend and warp fantastically. He snapped his eyelids shut, only to begin feeling the nightmarish bodily sensations once more. He felt the cot slowly rise longitudinally, felt himself upside down, then the snap of turning over him. Four elongated eyes peered at him. Attendants coming for to take me home.... "Touch me and I'll kick your teeth in!" he yelled. "I'm going to Terra. Wish you were going to Terra?" Then it was better. Oddly, he passed the twelfth day easily. By the fourteenth day, Craig knew he could stand Grav 1. The whine of the Most of the men had passed through the torments of gravitational conditioning. The huge headquarters base centrifuge aboard the man-made satellite had gradually caused their bodies to respond once more to a single source of pull. They were now ready to become inhabitants of planets again, instead of free-falling ships. On the eighteenth day, automatic machinery freed them from their imprisoning cots. Clumsily and awkwardly at first, the men began to and joked about it and kidded those who were slow at adjusting. Then they again began taking paraoxylnebutal in preparation for the free-fall flight to Terra. Only one of the score of men in the centrifuge tank remained voluntarily in his cot. "Space article violator," the old man informed Craig. "Psycho, I think. Went amuck with some extraterritorials. Killed a dozen." "What will they do, exile him?" "Not to Chociante, if that's what you mean. They just jerked his space card and gave him a one-way ticket to Terra." "And spend your weekends on Luna." Craig half rose from his cot, jarred into anger. But the old spaceman turned, smiling wryly. "Don't get hot, kid. I guess I spent too long in Zone V." He paused to examine his wrinkled hands. They were indelibly marked with lever callouses. "You get to thinking anyone who stays closer'n eighty light years from Terra is a System, matter of fact. Never saw much of anything close up. I stood it on and play spaceman. But Craig swore he'd make sure that the kid knew what a stinking life it was. At 1300 hours, the ferry bumped heavily alongside the starboard lock. It was the signal for relief in the passengers' quarters Orderly 12 handed him a message container. "Who's it from? Somebody on Terra?" "From a private spaceman named Morgan Brockman." " duty to the Universe? No, the old man had not been in Intergalactic. He had been a tramp spaceman. Well, why had planet Terra. He tried to recall his first thrill at seeing Los Angeles, 1500 square miles of it, from the ship as it entered the atmosphere. first physical contact with Terra had passed unnoticed. "Sir! Sir!" cried a voice behind him. you couldn't be expected to be familiar with Terra's fashions. In your present outfit you would certainly be typed as a ... well, you'd be made uncomfortable."

<question>:
What is the unspoken warning of the psychologist?

<options>:
A Even good jobs get boring on Terra.
B Private citizens do not enjoy the same rights as spacemen.
C The culture on Terra is radically different from the culture in space.
D The gravity on Terra could make a spaceman feel sick all the time.

<answer>:

C