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

<passage>:
They went back to the Nadine for weapons more adequate for thrashed out very painstakingly, in formal conference on the space-yacht painstakingly be brought across light-years of space to the new worlds From the viewpoint of the Nadine's to the same conclusion but he was not at all enthusiastic about their The humanity spread through the galaxy with an attendant train of insects and annoyances. If they left their pests behind, the total system of checks and balances which make life practical would get lopsided. It would not maintain itself. The vagaries that could result were admirably illustrated in and on the landscape outside the Nadine hydrochloric-acid ice. But the ice-cap was simple snow. Its size, too, told about temperature-distribution on the planet. A large cap would have meant a large area with arctic and sub-arctic temperatures, with wide tropical and sub-tropical zones. The fact was verified by the thick, dense cloud-masses which covered most of the surface,—all the surface, in fact, outside the ice-cap. But since there were ice-caps man could endure the air and temperature conditions he would find. approaching the world on planetary drive. He was to be left here, with such as are placed on certain worlds for the convenience of interstellar passage leading away. He called. But Moran observed with grudging respect that he didn't give him a chance to do anything drastic. These people on the Nadine indefinite distance in an indefinite direction from their last landing-point, and they had still to re-locate themselves. its space-port. With clearance-papers in order, they could land unquestioned at any other space-port and take off again—provided the other space-port was one they had clearance for. Without rigid control of space-travel, any criminal anywhere could escape the consequences of Nadine . The trouble was that the Wherever the yacht landed, such a disparity between its documents and effect, with six people on board instead of five, the Nadine could not land anywhere for supplies. With five on board, as her papers declared, space-port officials' suspicion of the rest. So he had to be dumped. picked at random for guidance. But the trip-tape had been computed for location was in doubt. It could have travelled at almost any speed in practically any direction for a length of time that was at least indefinite. A liner could re-locate itself without trouble. It had elaborate observational equipment and tri-di star-charts. But smaller craft had to depend on the Galactic Directory. The process would be to the way to find out where one was, when one's position became doubtful. The Nadine waved his hand at the speaker. "Listen!" that had that sound in it. It marked a first-landing spot on some planet Then we'd know where we are and how to get to Loris." signal's coming from, we'll take you somewhere near enough to the ice-cap to have an endurable climate. I've been figuring on food, too. That will depend on where we are from Loris because we have to keep enough for ourselves. But we can spare some. We'll give you the emergency-kit, anyhow." provide food in a minimum of time. It was not an encouraging thought, off-planet, and fast. But space-travel regulations are especially designed to prevent such escapes. space-traffic required a ship on landing to deposit its fuel-block in the space-port's vaults. The fuel-block was not returned until clearance for departure had been granted. But Moran had waylaid the messenger carrying the he still clung to hope of avoiding return—which Now the space-yacht moved toward a vast mass of fleecy whiteness without rest of the space-noises together. "Watch our height, Carol." course. Fifteen miles to surface below. Ten. Five. At twenty-five down it was pure opacity. Anything could exist in that dense, almost The Nadine in which one could see clearly nearby, less clearly at a little distance, and not at all beyond a quarter-mile or so. on which one would walk, which was strangest. It had color, but the the only considerable landmark within the half-mile circle in which The Nadine checked her downward motion. Interplanetary drive is rugged true silence. The space-yacht had come to rest possibly a hundred yards from the mound which was the source of the space-signal. That mound shared the peculiarity of the ground as far as they could see through much louder. Something hooted, maintaining the noise for an impossibly in landing. I've seen something like it somewhere, but never taking the finality. Moran said bitingly Nadine rested. The enigmatic, something. It blurred the shape it covered, very much as enormous "You won't have to live here," said Burleigh. "We'll take you somewhere explore." to get in the ship." rest of us wear suits. We don't know what that stuff is outside." Moran silently went to the space-suit rack and began to get into a suit. Modern space-suits weren't like the ancient crudities with bulging metal casings and enormous globular helmets. Non-stretch fabrics took the place of metal, and constant-volume joints were really practical nowadays. A man could move about in a late-model space-suit almost as easily as in ship-clothing. The others of the landing-party donned their special garments with the brisk absence of fumbling that these people displayed in every action. "I don't!" snapped Moran. He flipped the fastener of his suit. He felt all the openings catch. He saw the others complete their equipment. They took arms. So far they had door opened. It was not necessary to check the air specifically. The They filed out of the airlock. They stood on ash-covered stone, only slightly eroded by the processes which made life possible on this planet. They looked dubiously at the scorched, indefinite substance stone on which the Nadine wing-covers and flew away, droning loudly. The four men heard the sound above even the monstrous cacophony of cries and boomings and grunts and " They're—bugs! " she said incredulously. " They're beetles! They're twenty times the size of the beetles we humans have been carrying around the galaxy, but that's what they are! " operation was necessary before humanity could move in. A complete animals. But still terrestrial creatures had to be introduced if a before native and terrestrial living things settled down together. It large and monstrous under the conditions of a new planet. And the ground.... can find out where you are, and I can find out what's ahead of me." He climbed up on the unscorched surface. It was elastic. The parchment-like top skin yielded. It was like walking on a mass of springs. "We'd better spread out," added Moran, "or else we'll break through that does make sense." was uncertain, as on a trampoline. They staggered. They moved toward the by reaching forward with its fore-part, securing a foothold, and then arching its middle portion like a cat arching its back, to bring its color from one end to the other. Its manner of walking was insane but somehow sedate. " Moran said with savage precision "It's not a hunting creature on worlds where it's smaller. It's not likely to have turned deadly here. Come on!" He went forward over the singularly bouncy ground. The others followed. creature more widely than most. He said sardonically "This ship won't do anybody any good. It's old-style. That thick belt everywhere. "We're going to find that this wreck has been here a century creatures in their labyrinths of tunnels began to panic. Off to the men—the armed ones—moved back from the smoke. They wore space-helmets with him on board without his being detected as an extra member of the such-and-such fingerprints, voyaging in a space-yacht of such-and-such size and registration. The world they came from would claim them as " Look out! It's coming! Kill it! Kill it—. " , necessarily accepted as a member of her crew.

<question>:
Which term best describes the ease of space travel within the context of the passage?

<options>:
A complex
B evolving
C strict
D flexible

<answer>:

C