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 humans, each supposedly originating in strict seclusion on as many with a minimum of ten others 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 "Emmer, a Neanderthal type and our archeologist, is around the beginning of the scale. I'm from Earth, near the middle, though on Emmer's side. Meredith, linguist, is on the other side of the middle. And beyond her, toward the far end, is Kelburn, mathematician. There's 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 proved that some humans did originate on one planet, that there was an "I do think I love you," she said. "And if love's enough, I may marry you in spite of everything. But you'll have to watch out whose children "You're thinking of Earth," said Halden. "Humans require a certain kind 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." It was easy to understand the attitude. Man was the most numerous "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 change was almost imperceptible, but it was enough to indicate that he was interested. Kelburn went to the projector. "It would be easier if we knew all the stars in the Milky Way, but though we've explored only a small portion Way is rotating. And while stars in a given region tend to remain "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 time right." visionport, where another ship hung motionless in space beside them. "Do you mind if I ask other questions?" "Go ahead," Kelburn invited sardonically. "But if it's not math, you'd better ask Halden. He's the leader of the expedition." Halden flushed the sarcasm wasn't necessary. It was true that Kelburn was the most advanced human type present, but while there were differences, biological and in the scale of intelligence, it wasn't he'd been on several expeditions and this was Kelburn's first trip. Damn it, he thought, that rated some respect. The Ribboneer shifted his attention. "Aside from the sudden illness of him. Luckily, a ship was passing and we hailed it because it's four cent here and there for the crew pilot and scientist's share of the for me. And you can tell the ship to go on without me." He rubbed his Firmon of hydroponics slouched in, a tall man with scanty hair and an equal lack of grace. He seemed to have difficulty in taking his eyes off Meredith, though, since he was a notch or so above her in the "Then change it to suit him. He's in charge of the ship and knows more nothing mattered, and for the sake of alloying the lower with the wanted her. "Hydroponics is your job. There's nothing do except rebuild the ship from the hull inward." They couldn't set up a continuous watch and shoot the animals down because there weren't that many men to spare. Besides, the use of trying to protect than to the pest. He'd have to devise other ways. Sam Halden got up. "I'll take a look and see what I can do." "I'll come along and help," said Meredith, untwining her legs and leaning against him. "Your mistress ought to have some sort of privileges." He looked from Halden to Emmer and back again. "The hydroponics tech over while I ask questions." He turned to Emmer. "I'm curious about their camp." "I don't question your authority," crinkled Taphetta. "To me, all 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 it, so they built more elaborately than they did later on. One-story not a scrap of writing or a tool or a single picture. They covered a route estimated at thirty thousand light-years in less than five thousand years—and not one of them died that we have a record of." never stayed. They were pretty special people themselves, big and they needed in the entire Milky Way. Their science was tremendously plasm and left us, hoping that some of us would survive. Most of us independently and those who did were scattered equally among early and planets we live on and it's hard to say just what it is." "What happened to those who didn't develop space travel?" asked Taphetta. "We helped them," said Emmer. And they had, no matter who or what they were, biologically late atomic—because they were human. That was sometimes a frightening thing for non-humans, that the race stuck together. They weren't actually It was Halden who answered him. "There's the satisfaction of knowing where we came from." He'd have done it anyway, but it was better to have the pilot's "Why do we have to watch it on the screen?" asked Meredith, glancing up. "I'd rather be in hydroponics." Halden shrugged. "They may or may not be smarter than planetbound Lights dimmed in the distant hydroponic section and the screen with two crew members, each with his own peculiar screen, below which was a "Go in and get them," said Halden. "We don't want the pests to find out that the bodies aren't flesh." "It was realistic enough," said Meredith as the crewmen shut off their machines and went out. "Do you think it will work?" "It might. We had an audience." "Did we? I didn't notice." Meredith leaned back. "Were the puppets have to identify them as their species. If they're smart enough, they'll know the value of a knife, no matter who uses it." "That's part of our precautions. They'll never know until they try—and they'll never get away from the trap to try." "Very good. I never thought of that," said Meredith, coming closer. "I Here we go again, he thought drearily, sliding his arm around her. To her, I'm merely a passionate savage. The conflict was not new nor confined to them. In one form or another, it governed personal relations between races that were united against 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 lead me astray." "Why not make a play for Kelburn? If you're going to be scientific about it, he'd give you children of the higher type." "Kelburn." It didn't sound like a name, the way she said it. "I don't 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>:
Of the four main crew members, who are focused on the most in the story?

<options>:
A Kelburn and Halden
B Meredith and Emmer
C Halden and Meredith
D Kelburn and Meredith

<answer>:

C