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

<passage>:
learned of it the same way. Pop didn't even think of it again. It seemed Pop Young was the one known man who could stand life on the to have nothing to do with him. But Sattell undoubtedly dealt with it fully in his desperate writings back Pop matter-of-factly tended the to Earth. secret, but only partly. His name was Sattell and he had reason not to talk. Pop Young alone knew the whole truth, and he kept his mouth shut, too. It wasn't anybody else's Pop didn't even ask. Pop continued to search absorbedly for material with which to capture to recover the years that had been memory. Sattell still seemed necessary, and in his spare time he worked industriously at recovering some missing portions of his life that Sattell He thought often of Sattell, down We didn't come here for nothing!" happily tell himself that it feels delicious. Sometimes it does. But Sattell couldn't comfort himself so easily. He knew about Pop, up on the surface. He'd shipped out, least partly hysterical. It was the tension landed. Then nothing happened. Pop made his way toward it in savagery due to terror. But, guidance. Sattell got the shakes when he thought of Pop, and Pop rather probably knew it. Of course, by the children and some of the happiness it with what—say—Sattell might Sattell. The facts spoke for themselves. Pop had come back to consciousness about Pop Young's shack in cannisters in a hospital with a great wound in his head and no memory Even when Sattell—whimpering—signed shack, he was pretty certain about time he took the job tending the what had happened to his wife up for Lunar City, Pop tracked and children. They'd been murdered He'd pictured the complete set-up he set about trying to pick up the threads of the life he could no longer remember. He met Sattell quite by accident. Sattell looked familiar. Pop eagerly tried to ask him questions. And Sattell turned gray and frantically denied that he'd ever seen Pop before. All of which happened back on Earth and a long time ago. It seemed to Pop that the sight of Sattell had brought back some vague and cloudy memories. They were not sharp, though, and he hunted up Sattell Pop simply gaped. He couldn't And Sattell went into panic when he returned. Nowadays, by the Big Crack, Pop wasn't so insistent on seeing Sattell, but he was deeply concerned with quite take it in. Sattell helped bring back. Pop was a highly conscientious man. He took good care of his job. There was a "This," snapped the red-headed the recovery of the memories that by the edge of the Big Crack. Pop Pop gazed at the plastic, fascinated. The red-headed man leaned forward, snarling. He slashed Pop Bring them here! Understand?" Pop said numbly: "What the hell?" The red-headed man hit him "Then phone down to the mine! Tell Sattell I'm here and he can come on up! Tell him to bring any He leaned forward. His face was only inches from Pop Young's. It was seamed and hard-bitten and At such times Pop hardly thought of Sattell. He knew he had plenty Sattell knowing what had happened to his wife and children, but it was hearsay only. He had no memory of them at all. But Sattell stirred the lost memories. At first Pop followed absorbedly from city to city, He twitched all over. Then he wiped out by an axe-blow. He did recover a good deal. When Sattell fled to another continent, Pop followed struck cruelly again at Pop Young's face. He seemed filled with fury, at he'd felt about her—and some fugitive of course, Pop was helpless to resent it. There were no weapons on the Moon and the mention of Sattell's When Sattell frenziedly tried to deny knowledge of the murder in Tangier, Pop had come to remember both his mental images of his children. of his married life. him. By that time he was quite sure that Sattell was the man who'd killed his family. If so, Sattell had profited by less than two days' pay for wiping out everything that Pop possessed. But Pop wanted it back. He couldn't prove Sattell's guilt. There was no evidence. In any case, he didn't really want Sattell to die. If he did, there'd be no way to recover more lost memories. Sometimes, in the shack on the far side of the Moon, Pop Young had odd fancies about Sattell. There was Somehow, the mention of Sattell had detail. He knew Sattell. That part was simple. Sattell had planned this made his mind work better. It always multi-million-dollar coup, as a man in prison might plan his break. The man knew the routine here in every the mine, for example. In each two it was stolen for the journey here. Sattell's associates had had to if he shook it, and it was worth no more than so many pebbles. But sometimes Pop wondered if Sattell more than two men—with Sattell as could do nothing. and Pop and the colony together. "I'd guess," said Pop painstakingly, "that Sattell figured it out. He's probably got some sort of gun to grinned savagely at Pop. He held a The red-headed man checked "No," said Pop, "they'll do it anyhow. to scream. But not Pop. He'd come to the Moon in the first place because Sattell was here. Near Sattell, he found very nasty hand-weapon trained on young man with a young wife who tell Sattell a thing about it, if I were you. It'll save trouble. Just let him Pop's middle. dearly. And when he was near Sattell "Don't come in!" he said mockingly. "And I don't give a damn Sattell. He simply wanted to be near him because it enabled him to recover again to find out if he was right. Sattell, he suddenly recovered a completely new memory. On their first wedding anniversary, so long ago, the moonscape. Pop Young meticulously Pop reflected hungrily that it was If it had not been for his vacuum suit and the cannister he carried, Pop clearly when he thought of Sattell, so by keeping Sattell in mind he recovered shook and trembled. Pop said calmly: Sattell had no such device for adjusting anyhow, then, but living one mile underground from Pop Young was much worse. Sattell clearly remembered the crime Pop Young hadn't yet recalled. He considered that Pop had made no overt attempt to revenge some retaliation so horrible and lingering that it was worth waiting for. He came to hate Pop with an insane ferocity. And fear. In his mind the need to escape became an obsession But he was helpless. He couldn't leave. There was Pop. He couldn't kill Pop. He had no chance—and he was afraid. The one absurd, irrelevant thing he could do was write thumped under Pop Young's vacuum boots. He turned. fell, too. Wherefore most men tended own affairs with fascinated attention. But then an event occurred which bore directly upon Pop Young and Sattell and Pop Young's missing years. Somebody back on Earth promoted If we were able to tell about "We felt a shock! What happened? What do we do?" "Don't do a thing," advised Pop. It didn't seem to have anything to do with Pop or with Sattell. But it did. There were just two passenger section of the plastic. When it was carved, he'd paint it. While he worked, he'd think of Sattell, because missing portions of his life—the parts Sattell had managed to get Sattell had committed. He felt, somehow, that he wouldn't get that back until he'd recovered all the rest.

<question>:
What is the relationship between Sattell and Pop Young?

<options>:
A Sattell uses methods to help Pop recover his memories
B Sattell is trying to escape Pop, who believes he killed his family
C Sattell was Pop's neighbor back on Earth
D Sattell is Pop's son and the only witness who saw Pop murder his wife and other children

<answer>:

B