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

<passage>:
QUEST OF THIG "HORDE." He had blasted across trackless space to subdue a defenseless world—only to meet on Earth emotions that were more deadly than weapons. rod-like weapon of white metal and his pouches for food and specimens. The Orthan entered the narrow strip of trees and crossed to the little-used highway on the other side. Here he patiently sat down to wait for an Earthman or an Earthwoman to pass. His task now was to cruiser where his two fellows and himself would drain the creature's mentality of all its knowledge. In this way they could learn whether a planet was suited for colonization by later swarms of Orthans. Already they had charted over a hundred celestial bodies but of them all only three had proven worthy of consideration. This latest planet, 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 their love-life, their everything! So it was that the bodies of the Earthman and the Orthan were strapped "There is nothing more to learn," he informed his impassive comrades. "Now, let us get on with the plastic surgery that is required. My new body must return to its barbaric household before undue attention is 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. "Home again," whispered Ellen as she stood beside Thig twelve weeks quarters for almost three months. Strange thoughts were afloat in the chaos of his cool Orthan brain. 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 glory of thinking for himself and making his own decisions. He had 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 who nestled trustingly against his tense man's body and slept—the son of Ellen and the man he had destroyed. Thig groaned. He was a weakling to let sentimentality so get the better 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 the unquestioning worship of the Horde! Ortha at once. "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 exile them on one of the less desirable continents, Antarctica for example or Siberia? They are primitive humans even as our race was once "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 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." the Orthan's vital throat tubes. His fingers and thumb gouged deep into Kam's startled throat and choked off any cry for assistance before it could be uttered. Before Thig's eyes half of his comrade's body sloughed away into foul corruption that swiftly gave way to hardened blobs of dessicated 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 ancestors at times 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. The deadly attack of Thig his own violent avenging of Kam's death, and 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. So Thig shot him where he stood, mercifully, before that vacant mad stare set him, too, to gibbering and shrieking. Then he stepped over 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. 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 him from the parent ship. The sensation of free flight against his new body was strangely exhilerating and heady. It was the newest of the emotions he had experienced on Earth since that day, so many months before, when he had felt the warmness of Ellen's lips tight against his. He swung about to the port, watched the flaming drive-rockets of the great exploratory ship hurl it toward far-away Ortha, and there was no 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 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 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 West. He must remember that always. He had destroyed the real Terry and now, for the rest of his life, he must make up to the dead man's family. The knowledge that Ellen's love was not really meant for him would be a knife twisting in his heart but for her sake he must endure it. Her

<question>:
Why is Thig's return to Earth bittersweet?

<options>:
A His Orthan background will always be at odds with his new life.
B It's grueling to remember what he did to Terry, and to always have to be him now.
C Though he wants it, he'll never truly belong. He'll always be an otherworlder.
D He misses his life as an Orthan, even though he's come to enjoy Earth.

<answer>:

C