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

<passage>:
Korvin's arrival a necessity. They were well into the atomic era, and were on the verge of developing space travel. Before long they'd be settling the other planets of their system, and then the nearer stars. Planets. An invitation, the Comity was sure, which the Tr'en would not accept. Korvin stretched out on the cell's single bunk, a rigid affair which was hardly meant for comfort, and sighed. He'd had three days of isolation, with nothing to do but explore the resources of his own Korvin was all alone. True, every night the guards came in and gave him a concentrated lesson in the local language, but Korvin failed to get much pleasure out of that, being unconscious at the time. But now he was equipped to nobody to discuss it with. He changed position on the bunk and stared at the walls. The Tr'en were efficient But he was almightily bored, and about ready to tell anything to anyone, just for the chance at a little conversation. As he reached this dismal conclusion, the cell door opened. Korvin got up off the bunk in a hurry and spun around to face his visitor. The Tr'en was tall, and slightly green. Korvin didn't know why, and neither did anybody else. There were a lot of theories, slightly—but no more than slightly—and came into the cell, closing the door behind him. Korvin thought of jumping the Tr'en, but decided quickly against it. He was a captive, and it was unwise to assume that his captors had no more resources than the ones he saw: a small "I want nothing with you," Didyak said, leaning against the door-frame. "You have other questions?" Korvin sighed. "What are you doing here, then?" he asked. As conversation, it wasn't very choice but it was, he admitted, better approach to the smallest problems of everyday living was a little hard to get the hang of, Korvin told himself bitterly. He thought for a second. "Why did you come to me?" he said at last. and Didyak had used a specific meaning, roughly: "gain information from, by peaceful and vocal means." Korvin filed it away for future reference. "Why did the Ruler not come to me?" Korvin asked. Korvin shrugged, sighed and smoothed back his hair. "I obey the command of the Ruler," he said—another ritual. Everybody obeyed the 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. table near him, staring at Korvin and his guards. The guards stood on either side of their captive, looking as impassive as jade statues, six and a half feet high. 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 nodded hurriedly. "Our race is more ... more approximate," he said apologetically. dials, blinking lights, tubes and wires, and a seat with armrests and straps. It was obviously a form of lie-detector—and Korvin felt Being what they were, though, they could only be a menace. And Korvin's appreciation of the size of that menace was growing hourly. He hoped the lie-detector had been adjusted correctly. If it showed him telling an untruth, he wasn't likely to live long, and his adjusted satisfactorily to your physiology. The questioning will now continue." Korvin swallowed again. The test hadn't really seemed extensive enough 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. He hoped they were right. The Ruler was frowning at him. Korvin did his best to look receptive. "Why did you land your ship on this planet?" the Ruler said. "But it is not—not the truth we want," the Ruler said. Korvin shrugged. "I replied to your question," he said. "I did not —"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 gestured and they went out the door in a hurry. The Ruler looked down at Korvin. "You will find that you cannot trick us," he said. "You will find that such fiddling"— Korvin translated—"attempts will get you nowhere." Korvin devoutly hoped so. The experts in logic arrived shortly, and in no uncertain terms Korvin was given to understand that logical paradox was not going to confuse indicators of the lie-detector with great care. "What is your plan?" he said at last, in a conspiratorial whisper. "To answer your questions, truthfully and logically," Korvin said. Korvin was very glad that wasn't a question. It was, after all, the only logical deduction. a logical race makes use of a traitor, but a logical race does not trust him. "Sometimes," Korvin 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 The ruler sighed gently. "Explain this governor to us," he said. Korvin shrugged. "The explanation cannot be given to you." The Ruler turned to a group of his experts and a short muttered conversation took place. At its end the Ruler turned his gaze back to "I will not," Korvin said. It was the signal for another conference. With some satisfaction, Korvin noticed that the Tr'en were becoming slightly puzzled they were no longer moving and speaking with calm assurance. The Ruler had finished his conference. "You are attempting again to confuse us," he said. Korvin shook his head earnestly. "I am attempting," he said, "not to confuse you." "Then I ask for an answer," the Ruler said. Korvin shook his head. "If you insist," he said, "I'll try it. But you won't understand it." "Do you act against your own interests?" Korvin shrugged. "Not knowingly," he said. The Ruler flashed a look at the technicians handling the lie-detector. Korvin turned to see their One of the technicians chimed in: "The machine tells us—" "Then the machine is faulty," the expert said. "It will be corrected." Korvin wondered, as the technicians argued, how long they'd take studying the machine, before they realized it didn't have any defects to correct. He hoped it wasn't going to be too long homesick. It took three days—but boredom never really had a chance to set in. Korvin found himself the object of more attention than he had hoped for one by one, the experts came to his cell, each with a different method of resolving the obvious contradictions in his statements. Some of them went away fuming. Others simply went away, puzzled. On the third day Korvin escaped. It wasn't very difficult insoluble. And the Tr'en weren't capable of that sort of thinking. Korvin thanked his lucky stars that their genius had been restricted to the physical and mathematical. Any insight at all into the mental sciences would have given them the key to his existence, and his

<question>:
Why did the Tr'en leave Korvin's door unlocked and a weapon nearby?

<options>:
A They were so caught up trying to figure out  Korvin's answers that they became somewhat careless in guarding him.
B Their subconscious knew that Korvin was an insoluble problem. This same subconscious led them to provide resources for his escape so they wouldn't have to deal with him anymore.
C They were tired of the Ruler's dictatorship and intentionally provided resources for Korvin's escape in hopes that he would help them overthrow the Ruler.
D After their interview with Korvin, they determined he was wasteful and confusing, but not a threat. In order to avoid another confusing interaction with him, they simply provided resources for his escape.

<answer>:

B