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

<passage>:
She provocatively arched her back. Not even the women of Kelburn's race had a body like hers and she knew it. "Racially, there should be a chance," she said. "Actually, Kelburn and I would be infertile." "Can you be sure?" he asked, knowing it was a poor attempt to act unconcerned. not unexpected—non-humans tended to dismiss the data as convenient speculation and nothing more. "There are at least a hundred kinds of humans, each supposedly originating in strict seclusion on as many widely scattered planets. Obviously there was no contact throughout the ages before space travel— and yet each planetary race can interbreed with a minimum of ten others ! That's more than a legend—one hell of a lot more!" "It is impressive," admitted Taphetta. "But I find it mildly distasteful to consider mating with someone who does not belong to my species." "That's because you're unique," said Halden. "Outside of your own world, there's nothing like your species, except superficially, and that's true of all other creatures, intelligent or not, with the sole exception of mankind. Actually, the four of us here, though it's accidental, very nearly represent the biological spectrum of human development. wanted her. "I do think I love you," she said. "And if love's enough, I may marry a corresponding span of fertility. Emmer just misses being able to breed with my kind, but there's a fair chance that I'd be fertile with Meredith and a similar though lesser chance that her fertility may extend to Kelburn." Taphetta rustled his speech ribbons quizzically. "But I thought it was you in spite of everything. But you'll have to watch out whose children Besides what? She had a beautiful body that could bear superior children—and they might be his. of planet. It's reasonable to assume that, if men were set down on a hundred such worlds, they'd seem to fit in with native life-forms on a few of them. That's what happened on Earth unbroken line of evolution that could be traced back a billion years." "You're thinking of Earth," said Halden. "Humans require a certain kind proved that some humans did originate on one planet, that there was an toward the highest goal they could conceive of? Climbing over—no, through —everybody they could coerce, seduce or marry—onward and found. Instead, he evolved elsewhere and later was scattered throughout this section of the Milky Way." "And so, to account for the unique race that can interbreed across thousands of light-years, you've brought in the big ancestor," commented Taphetta dryly. "It seems an unnecessary simplification." "Can you think of a better explanation?" asked Kelburn. "Something had to distribute one species so widely and it's not the result of parallel evolution—not when a hundred human races are involved, and only the human race." others—and humans were more than a little feared. If they ever got together—but they hadn't except in agreement as to their common origin. Still, Taphetta the Ribboneer was an experienced pilot and could be very useful. A clear statement of their position was essential in helping him make up his mind. "You've heard of the adjacency mating principle?" asked Sam Halden. "Vaguely. Most people have if they've been around men." "We've got new data and are able to interpret it better. The theory is that humans who can mate with each other were once physically close. We've got a list of all our races arranged in sequence. If planetary race F can mate with race E back to A and forward to M, and race G is fertile only back to B, but forward to O, then we assume that whatever their positions are now, at once time G was actually adjacent to F, but "And that's the hypothetical route of the unknown ancestor?" "To the best of our knowledge," said Kelburn. "And whereas there are humans who are relatively near and not fertile, they can always mate with those they were adjacent to two hundred thousand years ago !" "The adjacency mating principle. I've never seen it demonstrated," murmured Taphetta, flexing his ribbons. "Is that the only era that satisfies the calculations?" mating scale, he shouldn't have been so interested. But his planet had been inexplicably slow in developing and he wasn't completely aware of his place in the human hierarchy. "Then change it to suit him. He's in charge of the ship and knows more evolution had taken a different course, but that he was in no sense humans hadn't developed as much as lower races and actually weren't prepared for the multitude of life-forms they'd meet in space. Firmon's "Hydroponics is your job. There's nothing completely her fault. Besides.... do except rebuild the ship from the hull inward." "I'll come along and help," said Meredith, untwining her legs and leaning against him. "Your mistress ought to have some sort of privileges." "Pests on the ship? It's filthy! My people would never tolerate it!" stretched their theories to cover the facts they had. "It was probably brought in with the supplies," said the biologist. "Considering how far we've come, it may have been any one of a half a dozen planets. Anyway, it hid, and since most of the places it had "But there are other worlds in which humans who were there before the Stone Age aren't related to anything else there. We have to conclude humans—late or early and male or female—look remarkably alike. If you are an archeologist, that's enough for me." He paused and flicked his speech ribbons. "Camp, did you say?" never stayed. They were pretty special people themselves, big and long-lived, and maybe they couldn't survive on any planet they found. Perhaps they had ways of determining there wasn't the kind of planet did." "This special planet sounds strange," murmured Taphetta. "Not really," said Emmer. "Fifty human races reached space travel independently and those who did were scattered equally among early and late species. It's well known that individuals among my people are often as bright as any of Halden's or Meredith's, but as a whole we And they had, no matter who or what they were, biologically late or early, in the depths of the bronze age or the threshold of atomic—because they were human. That was sometimes a frightening thing for non-humans, that the race stuck together. They weren't actually aggressive, but their total number was great and they held themselves aloof. The unknown ancestor again. Who else had such an origin and, it would have to be shared. That was what Taphetta had been afraid of—there was one kind of technical advancement that multiplied unceasingly. The race that could that the bodies aren't flesh." "It was realistic enough," said Meredith as the crewmen shut off their her, I'm merely a passionate savage. They went to his cabin. she knew as well as he that Earth was as advanced as her own world. She had something else in mind. "I don't think I will, though. We might have children." "Would it be wrong?" he asked. "I'm as intelligent as you. We wouldn't have subhuman monsters." The conflict was not new nor confined to them. In one form or another, it governed personal relations between races that were united against non-humans, but held sharp distinctions themselves. "I haven't asked you to marry me," he said bluntly. "Because you're afraid I'd refuse." It was true no one asked a member of a higher race to enter a permanent union. "Why did you ever have anything to do with me?" demanded Halden. "Love," she said gloomily. "Physical attraction. But I can't let it like him and he wouldn't marry me." "He wouldn't, but he'd give you children if you were humble enough. There's a fifty per cent chance you might conceive."

<question>:
What is NOT true of the crew?

<options>:
A They are all different species
B They are all focused on finding evidence to support an important theory
C They are all respected in their field
D They could all mate with each other (it was explicitly discussed as a possibility in the story)

<answer>:

D