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

<passage>:
Tr'en were an efficient people. All the preliminary reports had agreed on that their efficiency, as a matter of fact, was what had made Korvin stretched out on the cell's single bunk, a rigid affair which Korvin was all alone. discuss almost anything from philosophy to plumbing, but there was nobody to discuss it with. He changed position on the bunk and stared at the walls. The Tr'en were efficient up off the bunk in a hurry and spun around to face his visitor. The Tr'en was tall, and slightly green. He looked, as all the Tr'en did, vaguely humanoid—that is, if you Korvin didn't it was none of his business. The Tr'en regarded him narrowly through catlike pupils. "You are Korvin," he said. It was a ritual, Korvin had learned. "You are of the Tr'en," he replied. The green being nodded. "I am Didyak of the Tr'en," he said. Amenities over with, he relaxed slightly—but no more than slightly—and came into the cell, closing "What do you want with me?" Korvin said. The Tr'en speech—apparently there was only one language on the planet—was stiff and slightly awkward, but easily enough learned under drug hypnosis Korvin sighed. "What are you doing here, then?" he asked. As to get the hang of, Korvin told himself bitterly. He thought for a as it did the disclosure of the Tr'en fifty-eight teeth, mostly pointed. Korvin stared back impassively. "I have been ordered to come to you," Didyak said, "by the Ruler. The Ruler wishes to talk with from, by peaceful and vocal means." Korvin filed it away for future reference. "Why did the Ruler not come to me?" Korvin asked. "The Ruler is the Ruler," Didyak said, slightly discomfited. "You are to go to him. Such is his command." Korvin shrugged, sighed and smoothed back his hair. "I obey the command of the Ruler," he said—another ritual. Everybody obeyed the command of the Ruler. If you didn't, you never had a second chance to try. But Korvin meant exactly what he'd said. He was going to obey the commands of the Ruler of the Tr'en—and remove the Tr'en threat from the rest of the galaxy forever. That, after all, was his job. Korvin decided, much too much of a bad idea, even when the color contrast of the Tr'en themselves were figured in. The Ruler himself, a Tr'en over seven feet tall and correspondingly broad, sat in the great chair, his four fingers tapping gently on the table near him, staring at Korvin and his guards. The guards stood on Korvin wasn't attempting to escape. He wasn't pleading with the Ruler. He wasn't defying the Ruler, either. He was just answering questions. The Tr'en liked to have everything clear. They were a logical race. The Ruler had started with Korvin's race, his name, his sex—if any—and whether or not his appearance were normal for humanity. Korvin shrugged. "Some are over eight feet tall," he said, "and others under four feet." He used the Tr'en measurement scale, of course it ," he volunteered helpfully. "Approximately?" the Ruler growled. "We ask for precision here," he said. "We are scientific men. We are exact." Korvin nodded hurriedly. "Our race is more ... more approximate," he "Undoubtedly," Korvin agreed politely. "I'll try to do the best I can for you." "You will answer my questions," the Ruler said, "with exactitude." He "My job required it," Korvin said. Korvin shrugged again. "What I say is true," he announced. "Do you Korvin's appreciation of the size of that menace was growing hourly. "I am not," he said. The Ruler looked to his technicians for a signal, and nodded on to him. But, after all, the Tr'en knew their business, better than anyone else could know it. They had the technique and the logic and the training. "My job required it," Korvin said. Korvin looked sober. "Yes," he said. "What else does your job entail?" the Ruler said. The Ruler roared. "Do not waste time with the obvious!" he shouted. "Do not try to trick us Korvin shrugged. "I replied to your question," he said. "I did not Ruler," he said at last, in an approximation of his usual one. "But the Ruler will not be confused. We have experts in matters of logic"—the Tr'en word seemed to mean right-saying —"who will advise the Ruler. They will be called." Korvin's guards were standing around doing nothing of importance now that their captor was strapped down in the lie-detector. The Ruler The Ruler looked down at Korvin. "You will find that you cannot trick Korvin were so much primer material for the Tr'en. "They can be treated mathematically," one of the experts, a small emerald-green being, told Korvin thinly. "Of course, you would not understand the mathematics. The expert frowned horribly, showing all of his teeth. Korvin did his Korvin was very glad that wasn't a question. It was, after all, the the experts were clustered around the single chair. Korvin was "Sometimes," Korvin said. "It has other names?" the Ruler said. "It has no name," Korvin said truthfully. The Tr'en idiom was like the Earthly one "I do," Korvin said, "for convenience." "Who is it that governs?" the Ruler said. The key question had, at last, been asked. Korvin felt grateful that the logical Tr'en had determined to begin from the beginning, instead of going off after details of armament first Korvin shrugged. "The explanation cannot be given to you." Korvin shook his head earnestly. "I am attempting," he said, "not to The Ruler hesitated, then nodded. "Ask it," he said. "We shall answer it if we see fit to do so." Korvin tried to look grateful. "Well, then," he said, "what is your The Ruler beckoned to a heavy-set green being, who stepped forward from a knot of Tr'en, inclined his head in Korvin's direction, and began. "Our government is the only logical form of government," he said in a high, sweet tenor. "The Ruler orders all, and his subjects obey. In this way uniformity is gained, and this uniformity aids in the speed of possible action and in the weight of action. All Tr'en act instantly in the same manner. The Ruler is adopted by the previous Ruler in this way we are assured of a common wisdom and a steady won't understand it." The Ruler frowned. "We shall understand," he said. "Begin. Who governs you?" "None," Korvin said. Korvin nodded. "Yes." Korvin shrugged. "Not knowingly," he said. The Ruler flashed a look at the technicians handling the lie-detector. Korvin turned to see their ," Korvin said. "It means the rule of the people. There is no need for another ruler." One of the experts piped up suddenly. "The beings themselves rule each other?" he said. "This is clearly impossible for, no one being can have the force to compel acceptance of his commands. Without his Korvin wondered, as the technicians argued, how long they'd take Korvin found himself the object of more attention than he had hoped Korvin thanked his lucky stars that their genius had been restricted particular plan. That, and the political structure of the Tr'en. The same lack of insight let the Tr'en subconscious work on his messages, but he could send them. He sent one now. Mission accomplished the Tr'en aren't about to come marauding out into space too soon. They've been given food for thought—nice indigestible food that's going to stick in

<question>:
What is the best description of Korvin's job?

<options>:
A Land his ship on the Tr'en planet
B Ensure the Tr'en evolve in their thinking before they start interstellar travel
C Staying alive
D Obey the commands of the Ruler of the Tr'en

<answer>:

B