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

<passage>:
of drowsy, pastoral peace. Navigator Arthur Farrell—it was his turn to stand watch—was sitting at an open-side port with a magnoscanner ready but in spite of his vigilance he had not exposed a film when the Stryker and Gibson came out of their sleeping cubicles reluctantly, climate. Stryker blinked and yawned as he let himself through the port, butchery gets on my nerves." Stryker shielded his eyes with his hands against the glare of sun on water. "You know I can't do that, Arthur. These Arzians may turn out to be Fifth Order beings or higher, and under Terran Regulations our tampering with what may be a basic culture-pattern would amount to armed invasion. We'll have to crack that cackle-and-grunt language of theirs and learn something of their mores before we can interfere." Farrell turned an irritable stare on the incurious group of Arzians gathering, nets and fishing spears in hand, at the edge of the sheltering bramble forest. "What stumps me is their motivation," he said. "Why do the fools go out to that islet every night, when they must know damned well what will happen next morning?" Gibson answered him with an older problem, his square face puzzled. "For Stryker and Farrell traded baffled looks. The city had become something we were making planetfall, that's all." Gibson stiffened resentfully, but Farrell's voice cut his protest short. as usual, to stop the slaughter." A barrage of barbed tentacles lashed out of the foam and drove into the forest, ignoring the Earthmen, and lined the casting ledges along the Stryker threw up his hands. "I've a mountain of data to collate, and Arthur is off duty after standing watch last night. Help yourself, but you won't find anything." The scouter was a speeding dot on the horizon when Farrell crawled into his sleeping cubicle a short time later, leaving Stryker to mutter over a vague sense of something overlooked prodded irritatingly at the back of his had all but drowned before his fellows pulled him out with extended spear-shafts. Which meant that the fishers could not swim, else some would surely have gone in after him. And the Marco's crew had explored Arz exhaustively without finding any completed itself with automatic logic, almost rousing Farrell out of his doze. He fell asleep with the paradox unresolved. Stryker was still humped over his records when Farrell came out of his Stryker snorted. "He's scouring the daylight side now," Stryker said. "Arthur, I'm going to ground Gib tomorrow, much as I dislike giving him a direct order. He's got that phantom city on the brain, and he lacks the imagination to understand how dangerous to our assignment an obsession of that sort can be." Farrell shrugged. "I'd agree with you offhand if it weren't for Gib's bullheaded habit of being right. I hope he finds it soon, if it's here. I'll probably be standing his watch until he's satisfied." Stryker looked relieved. "Would you mind taking it tonight? I'm and packed his pipe, settling himself comfortably while Stryker mixed a of dull routine logwork had built up a need for physical action that chafed his temper he was intrigued and at the same time annoyed by the enigmatic relation that linked the Arzian fishers to the dragons and squids, and his desire to understand that relation was aggravated by the knowledge that Arz could be a perfect world for Terran colonization. That is, he thought wryly, if Terran colonists could stomach the weird custom pursued by its natives of committing suicide in pairs. He went over again the improbable drama of the past three mornings, and found it not too unnatural until he came to the motivation and the means He went inside again, and the sound of Stryker's muffled snoring fanned need help the audicom would summon Stryker. Investigating without the bramble he came upon a pair of Arzians curled up together on the He worked deeper into the underbrush and found other sleeping couples, center of the island without further discovery and was on the point of turning back, disgusted, when something bulky and powerful seized him A sharp sting burned his shoulder, wasp-like, and a sudden overwhelming lassitude swept him into a darkness deeper than the Arzian night. His last conscious thought was not of his own danger, but of Stryker—asleep and unprotected behind the but for some seconds his shuttling mind was too busy to consider the danger of predicament. Whatever brought me here anesthetized me first , he thought. That sting in my shoulder was like a hypo needle. more seconds passed before he gained control of himself, sweating with the belt and call Stryker.... He bent every ounce of his will toward raising his right hand, and failed. His arm was like a limb of lead, its inertia too great to budge. He relaxed the effort with a groan, sweating again when he saw a fiery against the inner curve of his elbow. He bent his will again toward motion this time the arm tensed a little, enough to send hope flaring through him. If he could put pressure enough against the stud.... "Stryker!" he yelled. "Lee, roll out— Stryker horror the tablet Stryker had mixed into his nightcap the night before. Worn out by his work, Stryker had made certain that he would not be easily disturbed. He tried again. "Stryker, help me! I'm on the islet!" Farrell fought down an insane desire to laugh. "Never mind that—get Gibson's voice came tinnily from the audicom. "Scattered them for the moment, Arthur—blinded the whole crew with the exhaust, I think. Stand fast, now. I'm going to pick you up." The scouter settled on the outcrop beside Farrell, so close that the hot The scouter swerved briefly as Gibson looked back. "You're all right, Arthur. Just hang on tight. I'll explain everything when we get you safe in the Marco ." Farrell forced himself to relax, more relieved than alarmed by the painful pricking of returning sensation. "I might have known it, damn , Gibson routed Stryker out of his cubicle and mixed drinks around, leaving Farrell comfortably relaxed in the padded control chair. The paralysis was still wearing off slowly, easing Farrell's fear of being permanently disabled. Stryker stared. "A marine city? What use would sea-creatures have for men or by a manlike race, judging from the architecture—and was submerged later by a sinking of land masses that killed off the original "Behold a familiar pattern shaping up," Stryker said. He laughed suddenly, a great irrepressible bellow of sound. "Arz is a squid's world, Arthur, don't you see? And like most civilized peoples, they're sportsmen. The flying-lizards are the game they hunt, and they raise the pink fishers for—" Farrell swore in astonishment. "Then those poor devils are put out there deliberately, like worms on a hook—angling in reverse! No wonder I couldn't spot their motivation!" "Colonization being out of the question, we may as well move on before the octopods get curious enough about us to make trouble. Do you feel up to the acceleration, Arthur?" Farrell and Stryker looked at each other, grinning. Farrell said: "You don't think I want to stick here and be used for bait again, do you?"

<question>:
What is the narrative purpose of having Arthur try to explore Arz while Stryker slept?

<options>:
A It was to increase the reader's curiosity because Arthur didn't know what the inside of the island looked like.
B It was to help the reader learn answers to the questions they had.
C It was to allow Arthur to communicate with the fishermen and learn more about their customs.
D It was to build suspense because Arthur was put in harm's way.

<answer>:

D