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

<passage>:
There were two pinkish, bipedal fishermen on the tiny landfall on the moonless Altarian but in spite of his vigilance he had not exposed a film when the bipedal Arzian fishermen posted on the tiny coral islet a quarter-mile offshore, their blank triangular faces turned stolidly toward the beach. climate. Stryker blinked and yawned as he let himself through the port, "Any sign of the squids yet?" he asked. gathering, nets and fishing spears in hand, at the edge of the sheltering bramble forest. that matter, what became of the city I saw when we came in through the stratosphere? It must be a tremendous thing, yet we've searched the entire globe in the scouter and found nothing but water and a scattering of little islands like this one, all covered with bramble. It wasn't a city these pink fishers could have built, either. The architecture was beyond them by a million years." Stryker and Farrell traded baffled looks. The city had become something irritating habit of being right—had worn their patience thin. "There never was a city here, Gib," Stryker said. "You dozed off while we were making planetfall, that's all." Gibson stiffened resentfully, but Farrell's voice cut his protest short. feet in length and a glistening chlorophyll green in the early light. They stooped like hawks upon the islet offshore, burying the two Arzian fishers instantly under their snapping, threshing bodies. Then around the outcrop the sea boiled whitely, churned to foam by a sudden uprushing of black, octopoid shapes. "The squids," Stryker grunted. "Right on schedule. Two seconds too late, A barrage of barbed tentacles lashed out of the foam and drove into the melee of winged lizards. The lizards took the air at once, leaving behind three of their number who disappeared under the surface like harpooned seals. No trace remained of the two Arzian natives. "A neat example of dog eat dog," Farrell said, snapping off the magnoscanner. "Do any of those beauties look like city-builders, Gib?" Chattering pink natives straggled past from the shelter of the thorn forest, ignoring the Earthmen, and lined the casting ledges along the beach to begin their day's fishing. "Nothing we've seen yet could have built that city," Gibson said stubbornly. "But it's here somewhere, and I'm going to find it. Will planetfall one of the pink fishers had fallen from a casting ledge into the water, and 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 slightest trace of boats or of boat landings. The train of association completed itself with automatic logic, almost rousing Farrell out of his doze. "I'll be damned," he muttered. "No boats, and they don't swim. Then how the devil do they get out to that islet? "Gibson found his lost city yet?" Farrell asked, and grinned when He's got that phantom city on the brain, and he lacks the imagination to atmosphere absorbed even starlight. He dragged a chair to the open port The Arzians did not swim, and without boats.... He stepped out through the open lock and paced restlessly up and down on the springy turf, feeling the ocean breeze soft on his face. Three days enigmatic relation that linked the Arzian fishers to the dragons and squids, and his desire to understand that relation was aggravated by the That is, he thought wryly, if Terran colonists could stomach the weird his whole fabric of speculation fell into a tangled snarl of inconsistencies. He gave it up finally how could any Earthman He went inside again, and the sound of Stryker's muffled snoring fanned clipped to the belt of his shorts. would show him how the natives reached the outcrop, and if he should Stryker's sanction was, strictly speaking, a breach of Terran "Damn Terran Regulations," he muttered. "I've got to Farrell snapped on the torch at the edge of the thorn forest and entered He worked deeper into the underbrush and found other sleeping couples, night-birds or scurrying rodents. He had worked his way close to the center of the island without further discovery and was on the point of turning back, disgusted, when something bulky and powerful seized him from behind. and unprotected behind the open port.... He was standing erect when he woke, his back to the open sea and a prismatic glimmer of early-dawn rainbow shining on the water before him. cried out hoarsely in sudden panic when he tried to turn his head and could not. He was on the coral outcropping offshore, and except for the involuntary muscles of balance and respiration his body was paralyzed. danger of predicament. Whatever brought me here anesthetized me first seconds passed before he gained control of himself, sweating with the failed. His arm was like a limb of lead, its inertia too great to budge. He On shore he could see the Marco Four resting between thorn forest and beach, its silvered sides glistening with dew. The port was still open, and the empty carrier rack in the bow told him that Gibson had not yet returned with the scouter. !" He tried again. "Stryker, help me! I'm on the islet!" outcrop just under the surface of the water, waiting with barbed tentacles spread and yellow eyes studying him glassily. He heard the with shock-born lucidity: water below, and felt his shaky laugh of relief stick in his throat. Two of the octopods were swimming strongly for shore, holding the rigid Arzian native carefully above water between them. Arthur. Just hang on tight. I'll explain everything when we get you safe in the painful pricking of returning sensation. "I might have known it, damn you," he said. "You found your lost city, didn't you?" Gibson sounded a little disgusted, as if he were still angry with himself over some private stupidity. "I'd have found it sooner if I'd had any brains. It was under water, of course." In the "We never saw the city from the scouter because we didn't go high enough," Gibson said. "I realized that finally, remembering how they used high-altitude blimps during the First Wars to spot submarines, and when I took the scouter up far enough there it was, at the ocean bottom—a city to compare with anything men ever built." Stryker stared. "A marine city? What use would sea-creatures have for buildings?" "None," Gibson said. "I think the city must have been built ages ago—by 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 builders and left Arz nothing but an oversized archipelago. The squids took over then, and from all appearances they've developed a culture of their own." race, and they're so far above Fifth Order that we're completely out of bounds here. Under Terran Regulations we can't colonize Arz. It would be "Invasion of a squid world?" Farrell protested, baffled. "Why should surface colonization conflict with an undersea culture, Gib? Why couldn't we share the planet?" "Because the octopods own the islands too, and keep them policed," the squid-people, making a dry-land canvass of his preserve here to pick couldn't spot their motivation!" Gibson got up and sealed the port, shutting out the soft morning breeze. "Colonization being out of the question, we may as well move on before blasted the

<question>:
How did the city get to be underwater?

<options>:
A Humans built it underwater
B The squid built it underwater
C Sea level rose up over it
D It was built on land then sank

<answer>:

D