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

<passage>:
Thig of Ortha was the vanguard of the conquering stupid face. It was as though he was looking into a bit of polished metal at the reflection of himself! The Earthman was opposite now and he must waste no more precious time. The mighty muscles of the Orthan sent him hurtling across the intervening space in two prodigious bounds, and his hands clamped going stale. He had sat every day for eight hours in front of that shiny-buttoned bane of the typist, but there were no results. Feebly clamping his throat relaxed for a moment and hacked along the side of his head. Blackness flooded the brain of Lewis, and he knew no more. their love-life, their everything! So it was that the bodies of the Earthman and the Orthan were strapped For ten hours or more the droning hum of the relay sucked Terry's brain dry of knowledge. The shock upon the nervous system of the Earthman proved too violent and his heart faltered after a time and stopped completely. Twice, with subtle drugs they restored pseudo-life to his body and kept the electrical impulses throbbing from his tortured brain, but after the third suspension of life Thig removed his helmet. "There is nothing more to learn," he informed his impassive comrades. dead man he knew, and confusion struck his well-trained brain. Men had no mates on Ortha, sex had been overthrown with all the other primitive impulses of barbarism so he was incapable of understanding and gunmen of his stories rendering him acutely unhappy. Sincerely he hoped that the west had reformed. Tonight or tomorrow night at the latest he must contact his two fellows and report that Earth was a planetary paradise. No other world, including Ortha, was so well-favored and rich. An expeditionary force to wipe the grotesque civilizations of Earth out of existence would, of course, be necessary before the first units of new Hordes could be landed. And there Thig balked. Why must they destroy these people, imperfect though their civilization might be, to make room for the Hordes? Thig tried to tell himself that it was the transmitted thoughts of the dead Earthman that made him feel so, but he was not too sure. For three months he had lived with people who loved, hated, wept and sacrificed for reasons that he had never known existed. He had learned the heady thought the same thoughts that a governor might think. Uncertainty added zest to every day's life. The Orthan had come to question the sole devotion of the individual to the Horde to the exclusion of all other interests. What, he wondered, would one new world—or a hundred—populated by the Hordes add to the progress of humanity? For a hundred thousand years the Orthan civilization had remained static, its energies directed into certain lived no longer. He mentally titled it: "Rustlers' Riot" and blocked in the outlines of his plot. One section of his brain was that of the sapping the life from his own brain. He knew that the story would never be written, but he toyed with the idea. So far had Thig the emotionless, robot-being from Ortha drifted from "I will recommend the conquest of this planet, 72-P-3 at once and the complete destruction of all biped life upon it. The mental aberrations of the barbaric natives might lead to endless complications if they were permitted to exist outside our ordered way of life. I imagine that three circuits of the planet about its primary should prove sufficient for the purposes of complete liquidation." "But why," asked Thig slowly, "could we not disarm all the natives and exile them on one of the less desirable continents, Antarctica for example or Siberia? They are primitive humans even as our race was once a race of primitives. It is not our duty to help to attain our own "Never again do I wish to set foot upon the soil of this mad planet. There are forces at work upon Earth that we of Ortha have long clutch of the sand about it, and they were rocketing skyward. Thig's broad fingers bit deep into the unyielding metal of his chair. Suddenly he knew that he must go back to Earth, back to Ellen and the children of the man he had helped destroy. He loved Ellen, and nothing must stand between them! The Hordes of Ortha must find some other world, an empty world—this planet was not for them. "Turn back!" he cried wildly. "I must go back to Earth. There is a woman there, helpless and alone, who needs me! The Horde does not need this planet." Kam's startled throat and choked off any cry for assistance before it matter. Horror for what he had done—that he had slain one of his own Horde—made his limbs move woodenly. All of his thoughts were dulled His body seemed paralyzed. This was the end, he thought as he waited stupidly for the blow to fall, the end for Ellen and the kids and all the struggling races of Earth. He would never write another cowboy yarn—they would all be dead anyhow soon. but to that very bit of unconscious atavism he now owed his life. A cool-headed robot of an Orthan would have efficiently used the blaster to destroy any possibility of remaining life in his unconscious body. why he had been left until last. Perhaps Torp wished to take cultures of his blood and tissues to determine whether a disease was responsible for his sudden madness. The deadly attack of Thig now the apparent return of the man he had killed come to life had all served to jolt his rigidly trained brain from its accustomed groove. The shock had been too much for the established thought-processes of the Orthan. the skeleton-thing that had been Torp, using the new strength that victory had given him to drive him along. He had saved a world's civilization from extinction! The thought sobered him yet, somehow, he was pleased that he had done so. After all, it had been the Earthwoman and the children he had been thinking of while he battled Kam, a selfish desire to protect them all. He went to the desk where Torp had been writing in the ship's log and read the last few nervously scrawled lines: Planet 72-P-3 unfit for colonization. Some pernicious disease that strikes at the brain centers and causes violent insanity is existent there. Thig, just returned from a survey of the planet, went mad and destroyed Kam. In turn I was forced to slay him. But it is not ended. body was strangely exhilerating and heady. It was the newest of the emotions he had experienced on Earth since that day, so many months regret in his mind that he was not returning to the planet of his first existence. He thought of the dull greys and blacks of his planet, of the monotonous routine of existence that had once been his—and his heart thrilled to the memories of the starry nights and perfect exciting days he had spent on his three month trip over Earth. He made a brief salute to the existence he had known, turned with a tiny sigh, and his fingers made brief adjustments in the controls. The He thought of many things in those few moments. He watched the roundness of Earth flatten out, then take on the cup-like illusion that all planets had for an incoming ship. He reduced the drive of his rockets to a mere whisper, striving to control the impatience that crowded his mind. He shivered suddenly, remembering his utter callousness the first time he had sent a space ship whipping down toward the hills and valleys below. And there was a sickness within him when he fully realized that, despite his acquired memory and traits, he was an alien from outer space. He fingered the tiny scars that had completely obliterated the slight deeply. There were tears in the depths of his eyes, then, and memories were hot, bitter pains. Earth was not far below him. As he let gravity suck him earthward, he heaved a gasp of relief. He was no longer Thig, a creature of a Horde's

<question>:
Why did Thig react with violence towards Kam while they were traveling back to Ortha?

<options>:
A He wanted to return to Earth and to Ellen.
B He did not want his blood tested for disease.
C He was angry that they had killed Lewis.
D He did not want to live on Earth any longer.

<answer>:

A