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

<passage>:
by JAMES Mac CREIGH Revolt was brewing on Venus, led by the descendant of the first Earthmen to land. Svan was the leader making the final plans—plotting them a bit too well. [Transcriber's Note: This etext was produced from Planet Stories Winter 1944. Extensive research did not uncover any evidence that ready to lift as soon as they come back." The Exec tossed away his cigarette. " If they come back." "Is there any question?" The Exec shrugged. "I don't know, Lowry," he said. "This is a funny Lowry lifted his eyebrows. "Oh? But after all, they're human beings, just like us—" "Not any more. Four or five generations ago they were. Lord, they don't even look human any more. Those white, flabby skins—I don't like them." "Acclimation," Lowry said scientifically. "They had to acclimate themselves to Venus's climate. They're friendly enough." Venusian mist. The native guard of honor, posted a hundred yards from the Earth-ship, stood stolidly at attention with their old-fashioned of us. I was in town yesterday, and I talked with some of the natives. They think there will be hordes of immigrants from Earth, now that we know Venus is habitable. And there's some sort of a paltry underground group that is spreading the word that the immigrants will drive the native Venusians—the descendants of the first expedition, that is—right down into the mud. Well—" he laughed—"maybe they will. After all, the fittest survive. That's a basic law of—" The annunciator over the open lock clanged vigorously, and a metallic their own mouths you have heard it. The Council was right." The younger of the two women sighed. She might have been beautiful, in spite of her dead-white skin, if there had been a scrap of hair on her head. "Svan, I'm afraid," she said. "Who are we to decide if this is a good thing? Our parents came from Earth. Perhaps there will be trouble at first, if colonists come, but we are of the same blood." Svan laughed harshly. " They alone will decide our course of action. We have agreed that, if the Earth-ship returns, it means disaster for Venus. Therefore, it must not return." Earth." "Never get back to Earth?" the old man gasped. "Has the Council authorized—murder?" feet, held up a shiny metal globe. "One of us will plant this in the ship. It will be set by means of this dial—" he touched a spot on the surface of the globe with a pallid finger—"to do nothing for forty hours. Then—it will explode. Atomite." He grinned triumphantly, looking from face to face. The grin faded uncertainly as he saw what was in their eyes—uncertainty, irresolution. Abruptly he set the bomb down, savagely ripped six leaves off a writing tablet on the table next him. He took a pencil and made a of her chair. It had held Venus-tobacco cigarettes there were a few left. She shook them out and handed the bowl to Svan, who was rapidly creasing the six fatal slips. He dropped them in the bowl, stirred it with his hand, offered it to the girl. "You first, Ingra," he said. himself took the last. All eyes were on him. No one had looked at their slips. has been to see it already. One will get out, at the best point we can find. It is almost dusk now. He can hide, surely, in the vegetation. The other five will start back. Something will go wrong with the car—perhaps it will run off the road, start to sink in the swamp. The guards will be called. There will be commotion—that is easy enough, after all a hysterical woman, a few screams, that's all there is to it. And the sixth person will have his chance to steal to the side of the ship. The bomb is magnetic. It will not be noticed in the dark—they will take off before sunrise, because they must travel away from the sun to return—in forty hours the danger is removed." There was comprehension in their eyes, Svan saw ... but still that uncertainty. Impatiently, he crackled: "Look at the slips!" Instinctively they had opened the slip, turned it over and over, striving to detect if it was the fatal one. They had felt nothing.... And his eyes saw nothing. The slip was blank. He gave it but a second's one to announce it—a second, ten seconds.... Then gray understanding came to him. A traitor! The six conspirators in Svan's old ground car moved slowly along the have ample time." Ingra? Her aunt? One of the men? The right answer leaped up at him. They all are , he thought. Not one of them understands what this means. They're afraid. present shower would deepen and intensify until midnight, then fall off again, to halt before morning. But before then they would be done. A proton-bolt lanced across the road in front of them. In the silence brakes. A Venusian in the trappings of the State Guard advanced on them Venus has no moon, and no star can shine through its vast cloud layer. the natives were dangerous. Spy-rays! They've been prohibited for the last three hundred years." "It isn't all the natives," Lowry said. "Look how they've doubled the guard around us. The administration is co-operating every way they Exec retorted. "They're all the same to me.... Look, your light's gone out now. Must have been the guard. They're on the wrong side to be coming from the town, anyhow...." were wise to circle around. Now, you know what you must do?" Ingra nodded, while the others remained mute. "We must circle back again," she parroted. "We are to wait five minutes, then drive the car It's not much of a plan. The guards would not be drawn away. I am glad I can't trust these five any more. If they must be destroyed, it is good that their destruction will serve a purpose. Aloud, he said, "You understand. If I get through, I will return to the the bomb will not explode until the ship is far out in space. Remember, , his mind echoed. He smiled. At least, they would feel no pain, never know what happened. With the amount of atomite in that bomb in the compartment, they would merely be obliterated in a ground-shaking crash. Abruptly he swallowed, reminded of the bomb that was silently counting off the seconds. "Go ahead," he ordered. "I will wait here." Was it an error that the girl should die with the others? There was an instant of doubt in his steel-shackled mind, then it was driven away. Perhaps she was loyal, yet certainly she was weak. And since he could not know which was the one who had received the marked slip, and feared to admit it, it was better they all should die. They would not be as easily overcome as the natives, not with those He had perhaps three minutes to wait he reckoned. His fingers went absently to the pouch in his wide belt, closed on the slip of paper. He turned it over without looking at it, wondering who had drawn the first delayed-action atomite bomb. There must have been another in the car, and it went off. They—they were planning to bomb us." "Amazing," the surgeon said dryly. "Well, they won't do any bombing "Better them than us," he said. "It's poetic justice if I ever saw it. They had it coming...." He paused thoughtfully, staring at a piece of paper between his fingers. "This is the only part I don't get," he said.

<question>:
How long did it take for Venus’s conditions to mutate its human colonies? What is the purpose of these mutations?

<options>:
A Three or four generations. Hunting.
B Four or five generations. Acclimation.
C Four or five generations. Bomb making.
D One or two generations. Revolution.

<answer>:

B